1869 + Interview Questions in IONIC-EQUILIBRIUM IN GENERAL AWARENESS Page 10 InterviewSolution

451.	Ionisation constant of `CH_(3)COOH` is `1.7 xx 10^(-5)` and concentration fo `H^(+)` in certain acetic acid solution is `3.4 xx 10^(-4) M` . The concentration of acetic acid solution isA. `3.4 xx 10^(-4)M`B. `3.4 xx 10^(-3)M`C. ``6.8 xx 10^(-4)M`D. `6.8 xx 10^(-3)M`
Answer» Correct Answer - D For a weak monobasric acid `K_(a)=Calpha^(2)` `K_(a)=C alpha.alpha=[H^(+)]alpha` `alpha=(K_(a))/([H^(+)])` `=(1.7 xx 10^(-4))/(3.4 xx 10^(-4)) =5 xx 10^(-2)` `C alpha =[H^(+)]=3.4 xx10^(-4)` `C=(3.4 xx 10^(-4))/(alpha)` `=6.8 xx 10^(-3) M`

Discussion

452.	For every diprotic acid of the type `H_(2)X`, how would you relate ionisation constant `K_(a1)` and `K_(a2)`A. `K_(a1)=K_(a2)`B. `K_(a1) lt K_(a2)`C. `K_(a2) lt K_(a1)`D. Data is insufficient
Answer» Correct Answer - C For diprotic acid `K_(a_(2))lt K_(a_(1))`.

Discussion

453.	Ionisation constant of `CH_(3)COOH` is `1.7xx10^(-5)` and concentration of `H^(+)ions` is `3.4xx10^(-4)`. Then, find out initial concentration of `CH_(3)COOH` molecules.A. `3.4xx10^(-4)`B. `3.4xx10^(-3)`C. `6.8xx10^(-4)`D. `6.8xx10^(-3)`
Answer» Correct Answer - D `CH_(3)COOH hArr CH_(3)COO^(-)+H^(+)` `K_(a)=([CH_(3)COO^(-)][H^(+)])/([CH_(3)COOH])` Given that, `[CH_(3)COO^(-)]=[H^(+)]=3.4xx10^(-4)M` `K_(a)` for `CH_(3)COOH=1.7xx10^(-5)` `CH_(3)COOH` is weak acid, so in it `[CH_(3)COOH]` is equal to initial concentration. Hence, `1.7xx10^(-5)=((3.4xx10^(-4))(3.4xx10^(-4)))/([CH_(3)COOH])` `[CH_(3)COOH]=(3.4xx10^(-4)xx3.4xx10^(-4))/(1.7xx10^(-5))` `=6.8xx10^(-3)M`

Discussion

454.	Which of the following statements about pH and `H^(+)` ion concentration is incorrect ?A. Addition of one drop of concentrated HCl in `NH_(4)OH` solution decreases pH of the solutionB. A solution of the mixture of one equivalent of each of `CH_(3)COOH` and NaOH has a pH of 7.C. pH of pure neutral water is not zeroD. A cold and concentrated `H_(2)SO_(4)` has lower `H^(+)` ion concentration than a dilute solution of `H_(2)SO_(4)`.
Answer» Correct Answer - B `CH_(3)COOH` is weak acid while NaOH is strong base, so one equivalent of NaOH cannot be neutralised with one equivalent of `CH_(3)COOH`. Hence, one equivalent of each does not have pH value 7. As the NaOH is a strong base, the solution will be basic having a pH more than 7.

Discussion

455.	Which of the following statements (s) is (are) correct?A. The `pH` of `1.0 xx 10^(-8)M` solution of `HCI` is `8`.B. The conjugate base of `H_(2)PO_(4)^(Theta)` is `HPO_(4)^(-2)`.C. Autoprotoysis constant of water increases with temperature.D. When a solution of weak monoprotic acid is titrated against a strong base, at half-neutralisation, point `pH =(1//2) pK_(a)`.
Answer» Correct Answer - B::C

Discussion

456.	The solubility of `AgI` in `NaI` solutions is less than that in pure water because:A. `AgI` forms complex with `NaI`B. Of common ion effectC. Solubility product of `AgI` is less than that of `NaI`.D. The temperature of the solution decreases.
Answer» Correct Answer - B

Discussion

457.	A 50.0 mL sample of a 1.00 M solution of a diprotic acid `H_(2)A(K_(a1)=1.0xx10^(-6) " and " K_(a2)=1.0xx10^(-10))` is titrated with 2.00 M NaOH. What is the minimum volume of 2.00 M NaOH needed to reach a pH of 10.00 ?A. 12.5 mLB. 37.5 mLC. 25.0 mLD. 50.0 mL
Answer» Correct Answer - b

Discussion

458.	Which one of the following is true for any diprotic acid, `H_(2)X`?A. `K_(a_(2))=K_(a_(1))`B. `K_(a_(2))gt K_(a_(1))`C. `K_(a_(2))lt K_(a_(1))`D. `K_(a_(2))=(1)/(K_(a_(1)))`
Answer» Correct Answer - C `H_(2)X hArr H^(+)+HX^(-)(K_(a_(1)))` `HX^(-)hArr +X^(2-)(K_(a_(2)))` In Ist equation hydrogen ion is formed from neutral molecule whereas in Iind equation it comes from negatively charged species. Due to negative charge removal of proton is difficult. So, `K_(a_(1))gt K_(a_(2))`

Discussion

459.	Which one of the following is true for any diprotic acid, `H_(2)X`?A. `K_(a_(2)) gt K_(a_(1))`B. `K_(a_(1)) gt K_(a_(2))`C. `K_(a_(2)) = (1)/(K_(a_(1)))`D. `K_(a_(2)) = K_(a_(1))`
Answer» Correct Answer - B

Discussion

460.	A solution of a weak monoprotic acid has dissociation constant `K_(a)`. The minimum initial concentration `C` such that the concentration of the undissociated acid can be equated to `C` within an error of `1%` would beA. `9900 K_(a)`B. `10000K_(a)`C. `99K_(a)`D. `K_(a)`
Answer» Correct Answer - A `K_(a) = (C alpha^(2))/((1-alpha))` For `%` error: `alpha = 0.01` `K_(a) = (C(0.01)^(2))/((1-0.01)) = (C xx 10^(-4))/(0.99)` `C rArr (K_(a)xx 0.99)/(10^(-4))` `rArr 9900 K_(a)`

Discussion

461.	`pOH` water is `7.0at 298 K`. If water is heated to `350K`, which of the following should be ture?A. `pOH` will decreaseB. `pOH` will increaseC. `pOH` will remain sevenD. Concentration of `H^(o+)` ions will increae but that of `overset(Theta)OH` will decrease.
Answer» Correct Answer - A On heating `H_(2)O` at `350K`, the selt ionisation of `H_(2)O`, increases `H_(2)O +H_(2)O hArr H_(3)O^(o+) + overset(Theta)OH` So the concentration of `[H_(3)O^(o+)]` and `[overset(Theta)OH]` both increases, so the `pH` increases or `pOH` decreases.

Discussion

462.	Assertion `(A ) :` Acetic acid is a weak acid Reason `(R ) :` Its conjugate base is weakA. Both A and R true and R is the correct explanation of AB. Both A and R are true but R is not a correct explanation of AC. A is true but R is falseD. A is false but R is true
Answer» Correct Answer - C

Discussion

463.	Conjugate base of `[Al(H_(2)O)_(6)]^(3+)` isA. `[Al(H_(2)O)_(5)OH]^(3+)`B. `[Al(H_(2)O)_(6)]^(2+)`C. `[Al(H_(2)O)_(5)OH]^(2+)`D. `[Al(H_(2)O)_(5)OH]^(+)`
Answer» Correct Answer - C

Discussion

464.	If the ionic product of water is `1.96 xx 10^(-14)` at `35^(0)C`,What is the value at `10^(0)C`A. `2.95 xx 10^(-14)`B. `1.96 xx 10^(-7)`C. `2.95 xx 10^(-15)`D. `3.9 xx 10^(-12)`
Answer» Correct Answer - C

Discussion

465.	The `K_(w)` for `2H_(2)O hArr H_(3)O^(+)_OH^(-)` changes from `10^(-14)` at `25^(@)C` to `9.62xx10^(-14)` at `60^(@)C`. What is pH of water at `60^(@)C` ? What happens to its neutrality ?
Answer» Correct Answer - `6.51`,

Discussion

466.	A cetrain ion `B^(-)` has an Arrhenius constant for basic character (eq. constnat `2.8xx10^(-7)`). The equilibrium constant for Lowry-Bronsed basic character is:A. `2.8xx10^(-7)`B. `3.57xx10^(-8)`C. `3.57xx10^(8)`D. `2.8xx10^(7)`
Answer» Correct Answer - D `B^(-)underset("Bronsted base")(+H^(+))hArr HB, K_(b)=2.8xx10^(-7)` `= ([HB])/([B^(-)][H^(+)])` …..(i) `B^(-)underset("Arrhenius base")(+H_(2)O)hArr HB+OH^(-)`, `K_(a)= ([HB][OH^(-)])/([B^(-)])` ….(ii) By eqs. (i) and (ii), `(K_(a))/(K_(b))= ([HB][OH^(-)])/([B^(-)])xx([B^(-)][H^(+)])/([HB])` `= [H^(+)][OH^(-)]= K_(w)` .....(iii) `:. K_(b)= (K_(a))/(K_(w)) = (2.8xx10^(-7))/(10^(-14))=2.8xx10^(7)`

Discussion

467.	The solubility product constant `(K_(sp))` of salts of types `MX, MX_(2)`, and `M_(3)X` at temperature `T` are `4.0 xx 10^(-8), 3.2 xx 10^(-14)`, and `2.7 xx 10^(-15)`, respectively. The solubilities of the salts at temperature `T` are in the orderA. `MXgt MX_(2)gt M_(3)X`B. `M_(3)gtMX_(2)gtMX`C. `MX_(2)gtM_(3)XgtMX`D. `MXgtM_(3)XgtMX_(2)`
Answer» Correct Answer - D `MX rarr underset(s)(M^(+))+underset(s)(X),` `K_(sp)=s^(2)` or `s=sqrt(K_(sp))=sqrt(4xx10^(-8))=2xx10^(-4)M` `MX_(x)hArr underset((s))(M^(2+))+underset((2s))(2X^(-)),` `K_(sp)=s(2s)^(2)=4s^(3)` `:. s=(K_(sp)//4)^(1//3)=((3/2xx10^(-14))/(4))^(1//3)=2 xx 10^(-5)M` `M_(3)X hArr underset(3s)(3M^(+))+underset(s)(X^(3-)),` `K_(sp)=(3s)^(3)s=27s^(4)` `:. s=((K_(sp))/(27))^(1//4)` `=(2.7 xx 10^(-15))/(27)=10^(-4)M` `:. MX gt M_(3)X gt Mx_(2)` `2 xx 10^(-4) gt 10^(-4) gt 2 xx 10^(-5)`

Discussion

468.	The solubility product constant `(K_(sp))` of salts of types `MX, MX_(2)`, and `M_(3)X` at temperature `T` are `4.0 xx 10^(-8), 3.2 xx 10^(-14)`, and `2.7 xx 10^(-15)`, respectively. The solubilities of the salts at temperature `T` are in the orderA. `MX gt MX_(2) gt M_(3)X`B. `M_(3)X gt MX_(2) gt MX`C. `MX_(2) gt M_(3)X gt MX`D. `MX gt M_(3)X gt MX_(2)`
Answer» Correct Answer - D Solubilities cannot be directly calculated because ail these salts have different formula. `{:("Salt","Solubility product","Solubility"),(MX,S^(2)=4.0 xx10^(-8),S=2 xx10^(-4)),(MX,4S^(3)=3.2 xx10^(-14),S=2 xx10^(-5)),(M_(3)X,27 S^(4)=2.7 xx10^(-15),S=1 xx10^(-4)):}` Order of solubility `= MX gt M_(2)X gt MX_(2)`

Discussion

469.	A solution of `CaF_(2)` is found to contain `4 xx 10^(-4)M` of `F^(Theta)`, `K_(sp)` of `CaF_(2)` isA. `3.2 xx 10^(-11)`B. `0.8 xx 10^(-11)`C. `6.4 xx 10^(-11)`D. `32 xx 10^(-11)`
Answer» Correct Answer - A `{:(CaF_(2)hArr,Ca^(2+),2F^(Theta)),(,x,2x):}` Total concentration of `[F^(Theta)] = 4 xx 10^(-4)M` `:.2x = 4 xx 10^(-4)` `x = 2 xx 10^(-4)` `:. K_(sp) = 4x^(3) = 4 xx (2xx 10^(-4))^(3) = 3.2 xx 10^(-11)`

Discussion

470.	At what `pH` will a `10^(-3)M` solution fo indicator with `K_(b) = 10^(-10)` changes colour?A. `10`B. `4.0`C. `3`D. `7`
Answer» Correct Answer - B An acid base indicator changes its colour when `pH = pK_(a) or pOH = pK_(b)`. `:. K_(b) = 10^(-10), pK_(b) = 10` `:. pOH = 10, pH = 14 - 10 = 4` `pH = 4`

Discussion

471.	From separate solution of four sodium salt NaW, Nax, NaY and NaZ had pH 7.0 , 9.0 , 10 . 0 and 11.0 respectively , when each solution was 0.1 M , the weakest acid is :-A. HWB. HXC. HYD. HZ
Answer» Correct Answer - 4

Discussion

472.	The `pH` of `0.1M` solution of the following salts decreases in the orderA. `HCl gt NaCl gt NH_(4)Cl gt NaCN`B. `HCl gt NaCN gt NH_(4)Cl gt NaCl`C. `NaCN gt NaCl gt NH_(4)Cl gt HCl`D. `NH_(4)Cl gt NaCN gt NaCl gt HCl`
Answer» Correct Answer - C `NaC1` (Salt of `S_(A)//S_(B)): pH = 7` `NaCN` (Salt of `W_(A)//S_(B)): pH gt 7` `HC1 (S_(A)): pH lt lt 7` `NH_(4)C1` (Salt of `S_(A)//W_(B)) : pH lt 7`. Hence the order is (c). `NaCN gt NaC1 gt NH_(4)C1 gt HC1`

Discussion

473.	The `pH` of `0.1M` solution of the following salts decreases in the orderA. `NaCI lt NH_(4) CI lt NaCN lt HCI`B. `HCI lt NH_(4) CI ltNaCI lt NaCN`C. `NaCN lt NH_(4) CI lt NaCI lt HCI`D. `HCI lt NaCIlt NaCN lt NH_(4) CI`
Answer» Correct Answer - B The Characterstics of the given solutions are: `NaCI` Neutral solution (Salt of `S_(A)//S_(B))` `NH_(4)CI` Slightly acidic sue to the reaction (Salt of `W_(B)//S_(A))` `NH_(4)^(o+) +NH_(4)OH +H^(o+)` `NaCN` Slightly alkaline due to the reaction (Salt of `S_(B)//W_(A))` `CN^(Theta) +H_(2)O hArr HCN +OH` `HCI` highly acidic The `pH` of the solution will follow the order highly acidic lt slightly acidic lt neutral lt slightly alkaline. i.e., `HCI lt NH_(4)CI lt NaCI lt NaCN`

Discussion

474.	It is found that `0.1M` solution of three sodium salts `NaX, NaY`, and `NaZ` have Ph 7.0, 9.0 and 11.0, respectively. Arrange the acids (HX, HY, and HZ) in order of increasing acidic character. Calculate dissociation constant of acids.
Answer» `{:(NaX+H_(2)Orarr"No hydrolysis",,"bacause",pH =7.0,),(NaY+H_(2)OrarrNaOH+HY,,,pH=9.0,),(NaZ+H_(2)OrarrNaOH+HZ,,,pH=11.0,):}` Thus, acidic character order for acids is : `HX gt HY gt HZ` Also for `NaY, [overset(Theta)OH] = 10^(-5) because pH = 9 :. pOH = 5` `Ch 10^(-5)` `C.sqrt((K_(h))/(c)) = 10^(-5)` or `C.sqrt((K_(h)xxC)/(K_(a))) = 10^(-5)` `(10^(-14)xx0.1)/(K_(a)) = 10^(-10), :. K_(a)` for `HY = 10^(-5)` Similarly, `K_(a) for HZ = 10^(-9)`

Discussion

475.	Four acids `HA,HB,HC` and `HD` form salts with `NaOH` of `Ph` 7,8,9 and 10 respectively when each solution was `0.1M`, the strongest acid is `:`A. `HA`B. `HB`C. `HC`D. `HD`
Answer» Correct Answer - 1 `{:("Salts",,pH),(NaA,,7),(NaB,,8),(NaC,,9),(NaD,,10):}` `A^(-)` is the weakest conjugate base. Hence, HA will be strongest acid

Discussion

476.	Which of the following salts will five highest pH in waterA. `Na_(2)CO_(3)`B. `CuSO_(4)`C. `KCl`D. `NaCl`
Answer» Correct Answer - A Salt of strong base and weak acid.

Discussion

477.	A solution has `pOH` equal to `13` at `298 K`. The solution will beA. Highly acidicB. Highly basicC. Moderatly basicD. Unpredictable
Answer» Correct Answer - A `pOH = 13, pH = 14 - 13 = 1`. Hence, solution is highly acidic.

Discussion

478.	From separate solutions of sodium salts, `NaW`, `NaX`, `NaY` and `NaZ` have `pH 7.0`, `9.0`, `10.0` and `11.0` respectively. When each solution was `0.1 M`, the strongest acid is:A. HWB. HXC. HYD. HZ
Answer» Correct Answer - a

Discussion

479.	The `pH` of `0.1M` solution of the following salts decreases in the orderA. NaCN lt `NH_4Cl` lt NaCN lt HClB. HCl lt `NH_4Cl` lt NCl lt NaCNC. NaCN lt `NH_4Cl` lt NaCl lt HClD. HCl lt NaCl lt NaCN lt `NH_4Cl`
Answer» Correct Answer - b

Discussion

480.	A pair of salts are given in a solution each is 0.1 M in concentration. Which solution has a higher pH ?A. NaCN and NaOBrB. NaF and NaOClC. NaF and NaOBrD. NaCN and NaOCl
Answer» Correct Answer - a

Discussion

481.	Which of the following salts will give highest `pH` in water?A. KClB. NaClC. `Na_(2)CO_(3)`D. `CuSO_(4)`
Answer» Correct Answer - C The highest pH refers to the basic solution containing `OH^(-)` ions. Therefore, the basic salt releasing more `OH^(-)` ions on hydrolysis will give highest pH in water. Only the salt of strong base and weak acid would release more `OH^(-)` ion on hydrolysis. Among the given salts, `Na_(2)CO_(3)` corresponds to the basic salt as it is formed by the neutralisation of NaOH [strong base] and `H_(2)CO_(3)` [weak acid]. `CO_(3)^(2-)+H_(2)O hArr HCO_(3)^(-)+OH^(-)`

Discussion

482.	In 0.02 M solution of perchlorid acid `(HClO_(4))` at 298 K the sum of pH and pOH is equal toA. 14B. 7C. between 6 and 7D. cannot be predicted
Answer» Correct Answer - A For any solution at 298 K , pH `+pOH =14`.

Discussion

483.	In aqueous solution, `H_(2)SO_(4)` and `HClO_(4)` are Equally strong. This is becauseA. Their basicities are sameB. Both are oxy acids of non-metalsC. Both have lower molecular weightsD. Levelling effect of water
Answer» Correct Answer - D Water levels all strong acids to the strengh of `H_(3)O^(+)`

Discussion

484.	Arrange the acids (I) `H_(2)SO_(3) (II) H_(3)PO_(3) (III) HClO_(3)` in the decreasing order of acidityA. `I gt III gt II`B. `I gt II gt III`C. `II gt III gt I`D. `III gt I gt II`
Answer» Correct Answer - D Acidity is directly proportional to oxidation number. As the O. No. of S, P and Cl in `H_(2)SO_(3), H_(3)PO_(4)` & `HClO_(3)` is +4, +3 & +5 repsectively so decreasing order of acidity will be `III gt I gt II`.

Discussion

485.	Match column-I (Solution of salts of salts of...) with column-II (pH of the solution is given by):
Answer» Correct Answer - a-s; b-r; c-q; d-p

Discussion

486.	Which of the following salts when added to pure water will not alter its `P^(H)`A. Ammonium cyanideB. Ferric chlorideC. Potassium cyanideD. Borax
Answer» Correct Answer - A `NH_(4)CN` is a salt of weak acid and weak base and `k_(a) = k_(b)`

Discussion

487.	The hydronium ion concentration in pure water is `1xx10^(-7) ` mol `L^(-1)`. The degree of dissociation of water isA. `1.8 xx 10^(-9)`B. `0.8 xx 10^(-8)`C. `9.8 xx 10^(-6)`D. `3xx10^(-9)`
Answer» Correct Answer - A If `alpha` is degree of dissociation `H_(2)OhArr H^(+) +OH^(-)` Initial conc. `C mol L^(-1)` Equi. Conc. `C(a-alpha)" "Calpha" "Calpha` `[H^(+)]=Calpha` or `alpha=([H^(+)])/(C )=(1xx10^(-7))/(55.5)` `=1.8 xx 10^(-9)`

Discussion

488.	Our of `HClO_(4)` and `H_(2)SO_(4)`, which is a stronger acid in an aqueous solutionA. `HClO_(4)`B. `H_(2)SO_(4)`C. Both are equally strongD. Strength depends on concentration
Answer» Correct Answer - C Factual question.

Discussion

489.	The pH of the solutions produced by mixing equal volumes of `2.0 xx 10^(-3) M HClO_(4)` and `1.0 xx 10^(-2) MKClO_(4)` isA. 2.7B. 2.3C. `3.0`D. `1.0`
Answer» Correct Answer - C `H^(+)` ions obtained only from `HClO_(4)` which ionises completely ( being a strong acid ). Equal volume of `KClO_(4)` solution added reduces `(H^(+))` ions to half `3.0` `:. \|H^(+)\|=(2xx10^(-3))/(2)` Hence `pH =-log (10^(-3))=3.0`

Discussion

490.	Which of the following salts will not undergo hydrolysis in water?A. Sodium sulphateB. Ammonium sulphateC. Aluminimum sulphateD. All the salts will hydrolyse
Answer» Correct Answer - A Salt of `S_(A)//S_(B)` do not undergo hydrolysis. So `Na_(2)SO_(4)` is a salt of `S_(A)//S_(B)`.

Discussion

491.	Which of the following salts will not change the `pH` of pure water on dissociation?A. `KCI`B. `AICI_(3)`C. `Na_(2)CO_(3)`D. `AI_(2)(SO_(4))_(3)`
Answer» Correct Answer - A Salt of `S_(A)//S_(B)` do not hydrolyse in `H_(2)O`. So `pH` does not change on adding KCI to `H_(2)O`.

Discussion

492.	The following equilibrium is established when `HC1O_(4)` is dissolved in weak acid `HF`, `HF+HClO_(4)hArrClO_(4)^(-)+H_(2)F^(+)` Which of the following is correct set of conjugate acid base pair?A. `HF` and `HCIO_(4)`B. `HF` and `CIO_(4)^(-)`C. `HF` and `H_(2)F`D. `HCIO_(4)` &`H_(2)F^(+)`
Answer» Conjugate acid base pair are differ by an proton `(H^(+))` `underset(acid)(H_(2)F^(+))overset(-H^(+))rarr underset(base)(HF)`

Discussion

493.	In the following reaction `HC_(2)O_(4)^(-)(aq)+PO_(4)^(3-)(aq)hArrHPO_(4)^(-2)(aq)+C_(2)O_(4)^(2-)(aq)`, which are the two Bronsted bases?A. `HC_(2)O_(4)^(-)` and `PO_(4)^(3-)`B. `HPO_(4)^(2-)` and `C_(2)O_(4)^(2-)`C. `PO_(4)^(3-)` and `C_(2)O_(4)^(2-)`D. `HC_(2)O_(4)^(-)` and `HPO_(4)^(2-)`
Answer» Correct Answer - C Both possess the tendency to accept proton.

Discussion

494.	The solubility of `CaCO_(3)` is `7mg//L`. Calculate the `K_(sp)` of `BaCO_(3)` whne `Na_(2)CO_(3)` is added slowely a solution containing equimolar concentration of `Ca^(2+)` and `Ba^(2+)` and no precipitate is formed until `90%` of `Ba^(2+)` has beem precipitated as `BaCO_(3)`.
Answer» Correct Answer - `4.9xx10^(-10);`

Discussion

495.	To separate and identify the ionis in a mixutre that may contain `Pb^(2+), Cu^(2+)` and `Mg^(2+)` use the reagents `H_(2)S, HCI` and NaOH. They should be added in the order:A. `HCI, H_(2)S, NaOH`B. `H_(2)S, HCI, NaOH`C. `HCI, NaOH, H_(2)S`D. `NaOH, H_(2)S, HCI`
Answer» Correct Answer - A HCI precipitates `Pb^(2+)` only, `H_(2)S` precipitates `Pb^(2+)` and `Cu^(2+)` and `NaOH precipitates all.

Discussion

496.	Among the mixutre (i) `50 ml` of `N//10 HCl + 50 ml` of `N//10 NaOH` (ii) `55 ml` of `N//10 HCl + 45 ml` of `N//10 NaOH` (iii) `75 ml` of `N//10 HCl + 25 ml` of `N//10 NaOH` (iv) `30 ml` of `N//5 HCl + 70 ml` of `N//5 NaOH` For how many of the above mixutres pH lies between 1 to 7
Answer» Correct Answer - 2

Discussion

497.	The solubility product of a soluble salt `A_(x)B_(y)` is given by: `K_(SP)= [A^(y+)]^(x) [B^(x-)]^(y)`. As soon as the product of concentration of `A^(y+)` and `B^(x-)` increases than its `K_(SP)`, the salt start precipitation. It may practically be noticed that AgCI is more soluble in water and its solublity decreases dramatically in `0.1M NaCI` or `0.1M AgNO_(3)` solution. It may therefore be conncluded that in presence of a common ion, the solubiolity of salt decreases. Equal volumes of two solutions are mixed. The one in which `CaSO_(4) (K_(SP)= 2.4xx10^(-5))` is precipitated, is :A. `0.02M CaCI_(2)+0.0004M Na_(2)SO_(4)`B. `0.01M CaCI_(2)+0.0004M Na_(2)SO_(4)`C. `0.02M CaCI_(2)+0.0002M Na_(2)SO_(4)`D. `0.03M CaCI_(2)+0.004M Na_(2)SO_(4)`
Answer» Correct Answer - D `[Cu^(2+)][SO_(4)^(2-)]= (0.03xxV)/(2V)xx[(0.004xxV)/(2V)]` `=3xx10^(-5)gt K_(SP)` Thus precipitation.

Discussion

498.	The ionisation constant of dimethylamine is `5.4xx10^(-4)`. Calculate its degree of ionization in its `0.02M` solution. What percentage of dimethylamine is ionized if the solution is also `0.1 M` in `NaOH`?
Answer» `underset("base")((CH_(3))_(2)NH_(2))+H_(2)O hArr underset("acid")((CH_(3))_(2)NH_(3)^(+))+OH^(-)` `K_(b)= ([(CH_(3))_(2)NH_(3)^(+)][OH^(-)])/([(CH_(3))_(2)NH_(2)])` `= (Calpha. Calpha)/(C(1-alpha))=(Calpha^(2))/((1-alpha))` `5.4xx10^(-4)=0.02xxalpha^(2)` Since `alpha gt 0.05`, we will use `K_(b) = (C alpha^(2))/((1-alpha))` or `5.4xx10^(-4)= (0.02xxalpha^(2))/((1-alpha))` Now `alpha = 0.151` In presence of `NaOH`, the dissociation of diethylamine will decrease due to common ion effect. Thus `0.1+Calpha = 0.1` and `1-alpha ~= 1` Thus `K_(b)= 5.4xx10^(-4)= (Calphaxx(0.1+Calpha))/(C(1-alpha))` or `alpha= 5.4xx10^(-3) = 0.0054`

Discussion

499.	The solubility product of a soluble salt `A_(x)B_(y)` is given by: `K_(SP)= [A^(y+)]^(x) [B^(x-)]^(y)`. As soon as the product of concentration of `A^(y+)` and `B^(x-)` increases than its `K_(SP)`, the salt start precipitation. It may practically be noticed that AgCI is more soluble in water and its solublity decreases dramatically in `0.1M NaCI` or `0.1M AgNO_(3)` solution. It may therefore be conncluded that in presence of a common ion, the solubiolity of salt decreases. Which of the following statement is wrong ? (1) `K_(SP)` of a salt depends upon temperature (2) `K_(SP)` of a salt has no units (3) The `K_(SP)` of salt `A_(x)B_(y)` can be given as: `x^(x).y^(y)(S)^(x+y)` (4) Solubility of `BaF_(2)` in a solution of `Ba(NO_(3))_(2)` can be given by `(1)/(2)[F^(-)]`A. 1B. 2C. 3D. 4
Answer» Correct Answer - B `K_(SP)` has unit `["mole lirtre"^(-1)]^(x+y)`

Discussion

500.	The solubility product of a soluble salt `A_(x)B_(y)` is given by: `K_(SP)= [A^(y+)]^(x) [B^(x-)]^(y)`. As soon as the product of concentration of `A^(y+)` and `B^(x-)` increases than its `K_(SP)`, the salt start precipitation. It may practically be noticed that AgCI is more soluble in water and its solublity decreases dramatically in `0.1M NaCI` or `0.1M AgNO_(3)` solution. It may therefore be conncluded that in presence of a common ion, the solubiolity of salt decreases. The pH of a saturated solution of `Mg(OH)_(2)` is: `(K_(SP) of Mg(OH)_(2)= 1xx10^(-11))`A. 9B. `3.87`C. `10.43`D. 5
Answer» Correct Answer - C `Mg(OH)_(2)hArr underset(S)(Mg^(2+))+underset(2S)(2OH^(-)) (K_(SP)=4S^(3))` `[OH^(-)]=2S=2xx3sqrt((K_(SP))/(4))` `= 2xx3sqrt((1xx10^(-11))/(4))` `=2xx1.36xx10^(-4)= 2.72xx10^(-4)` `:. pOH = 3.565` `:. pH=10.435`

Discussion

Explore topic-wise InterviewSolutions in .

Ionisation constant of `CH_(3)COOH` is `1.7 xx 10^(-5)` and concentration fo `H^(+)` in certain acetic acid solution is `3.4 xx 10^(-4) M` . The concentration of acetic acid solution isA. `3.4 xx 10^(-4)M`B. `3.4 xx 10^(-3)M`C. ``6.8 xx 10^(-4)M`D. `6.8 xx 10^(-3)M`

For every diprotic acid of the type `H_(2)X`, how would you relate ionisation constant `K_(a1)` and `K_(a2)`A. `K_(a1)=K_(a2)`B. `K_(a1) lt K_(a2)`C. `K_(a2) lt K_(a1)`D. Data is insufficient

Ionisation constant of `CH_(3)COOH` is `1.7xx10^(-5)` and concentration of `H^(+)ions` is `3.4xx10^(-4)`. Then, find out initial concentration of `CH_(3)COOH` molecules.A. `3.4xx10^(-4)`B. `3.4xx10^(-3)`C. `6.8xx10^(-4)`D. `6.8xx10^(-3)`

The solubility of `AgI` in `NaI` solutions is less than that in pure water because:A. `AgI` forms complex with `NaI`B. Of common ion effectC. Solubility product of `AgI` is less than that of `NaI`.D. The temperature of the solution decreases.

A 50.0 mL sample of a 1.00 M solution of a diprotic acid `H_(2)A(K_(a1)=1.0xx10^(-6) " and " K_(a2)=1.0xx10^(-10))` is titrated with 2.00 M NaOH. What is the minimum volume of 2.00 M NaOH needed to reach a pH of 10.00 ?A. 12.5 mLB. 37.5 mLC. 25.0 mLD. 50.0 mL

Which one of the following is true for any diprotic acid, `H_(2)X`?A. `K_(a_(2))=K_(a_(1))`B. `K_(a_(2))gt K_(a_(1))`C. `K_(a_(2))lt K_(a_(1))`D. `K_(a_(2))=(1)/(K_(a_(1)))`

Which one of the following is true for any diprotic acid, `H_(2)X`?A. `K_(a_(2)) gt K_(a_(1))`B. `K_(a_(1)) gt K_(a_(2))`C. `K_(a_(2)) = (1)/(K_(a_(1)))`D. `K_(a_(2)) = K_(a_(1))`

A solution of a weak monoprotic acid has dissociation constant `K_(a)`. The minimum initial concentration `C` such that the concentration of the undissociated acid can be equated to `C` within an error of `1%` would beA. `9900 K_(a)`B. `10000K_(a)`C. `99K_(a)`D. `K_(a)`

`pOH` water is `7.0at 298 K`. If water is heated to `350K`, which of the following should be ture?A. `pOH` will decreaseB. `pOH` will increaseC. `pOH` will remain sevenD. Concentration of `H^(o+)` ions will increae but that of `overset(Theta)OH` will decrease.

Assertion `(A ) :` Acetic acid is a weak acid Reason `(R ) :` Its conjugate base is weakA. Both A and R true and R is the correct explanation of AB. Both A and R are true but R is not a correct explanation of AC. A is true but R is falseD. A is false but R is true

Conjugate base of `[Al(H_(2)O)_(6)]^(3+)` isA. `[Al(H_(2)O)_(5)OH]^(3+)`B. `[Al(H_(2)O)_(6)]^(2+)`C. `[Al(H_(2)O)_(5)OH]^(2+)`D. `[Al(H_(2)O)_(5)OH]^(+)`

If the ionic product of water is `1.96 xx 10^(-14)` at `35^(0)C`,What is the value at `10^(0)C`A. `2.95 xx 10^(-14)`B. `1.96 xx 10^(-7)`C. `2.95 xx 10^(-15)`D. `3.9 xx 10^(-12)`

The `K_(w)` for `2H_(2)O hArr H_(3)O^(+)_OH^(-)` changes from `10^(-14)` at `25^(@)C` to `9.62xx10^(-14)` at `60^(@)C`. What is pH of water at `60^(@)C` ? What happens to its neutrality ?

A cetrain ion `B^(-)` has an Arrhenius constant for basic character (eq. constnat `2.8xx10^(-7)`). The equilibrium constant for Lowry-Bronsed basic character is:A. `2.8xx10^(-7)`B. `3.57xx10^(-8)`C. `3.57xx10^(8)`D. `2.8xx10^(7)`

A solution of `CaF_(2)` is found to contain `4 xx 10^(-4)M` of `F^(Theta)`, `K_(sp)` of `CaF_(2)` isA. `3.2 xx 10^(-11)`B. `0.8 xx 10^(-11)`C. `6.4 xx 10^(-11)`D. `32 xx 10^(-11)`

At what `pH` will a `10^(-3)M` solution fo indicator with `K_(b) = 10^(-10)` changes colour?A. `10`B. `4.0`C. `3`D. `7`

From separate solution of four sodium salt NaW, Nax, NaY and NaZ had pH 7.0 , 9.0 , 10 . 0 and 11.0 respectively , when each solution was 0.1 M , the weakest acid is :-A. HWB. HXC. HYD. HZ

The `pH` of `0.1M` solution of the following salts decreases in the orderA. `HCl gt NaCl gt NH_(4)Cl gt NaCN`B. `HCl gt NaCN gt NH_(4)Cl gt NaCl`C. `NaCN gt NaCl gt NH_(4)Cl gt HCl`D. `NH_(4)Cl gt NaCN gt NaCl gt HCl`

The `pH` of `0.1M` solution of the following salts decreases in the orderA. `NaCI lt NH_(4) CI lt NaCN lt HCI`B. `HCI lt NH_(4) CI ltNaCI lt NaCN`C. `NaCN lt NH_(4) CI lt NaCI lt HCI`D. `HCI lt NaCIlt NaCN lt NH_(4) CI`

It is found that `0.1M` solution of three sodium salts `NaX, NaY`, and `NaZ` have Ph 7.0, 9.0 and 11.0, respectively. Arrange the acids (HX, HY, and HZ) in order of increasing acidic character. Calculate dissociation constant of acids.

Four acids `HA,HB,HC` and `HD` form salts with `NaOH` of `Ph` 7,8,9 and 10 respectively when each solution was `0.1M`, the strongest acid is `:`A. `HA`B. `HB`C. `HC`D. `HD`

Which of the following salts will five highest pH in waterA. `Na_(2)CO_(3)`B. `CuSO_(4)`C. `KCl`D. `NaCl`

A solution has `pOH` equal to `13` at `298 K`. The solution will beA. Highly acidicB. Highly basicC. Moderatly basicD. Unpredictable

From separate solutions of sodium salts, `NaW`, `NaX`, `NaY` and `NaZ` have `pH 7.0`, `9.0`, `10.0` and `11.0` respectively. When each solution was `0.1 M`, the strongest acid is:A. HWB. HXC. HYD. HZ

The `pH` of `0.1M` solution of the following salts decreases in the orderA. NaCN lt `NH_4Cl` lt NaCN lt HClB. HCl lt `NH_4Cl` lt NCl lt NaCNC. NaCN lt `NH_4Cl` lt NaCl lt HClD. HCl lt NaCl lt NaCN lt `NH_4Cl`

A pair of salts are given in a solution each is 0.1 M in concentration. Which solution has a higher pH ?A. NaCN and NaOBrB. NaF and NaOClC. NaF and NaOBrD. NaCN and NaOCl

Which of the following salts will give highest `pH` in water?A. KClB. NaClC. `Na_(2)CO_(3)`D. `CuSO_(4)`

In 0.02 M solution of perchlorid acid `(HClO_(4))` at 298 K the sum of pH and pOH is equal toA. 14B. 7C. between 6 and 7D. cannot be predicted

In aqueous solution, `H_(2)SO_(4)` and `HClO_(4)` are Equally strong. This is becauseA. Their basicities are sameB. Both are oxy acids of non-metalsC. Both have lower molecular weightsD. Levelling effect of water

Arrange the acids (I) `H_(2)SO_(3) (II) H_(3)PO_(3) (III) HClO_(3)` in the decreasing order of acidityA. `I gt III gt II`B. `I gt II gt III`C. `II gt III gt I`D. `III gt I gt II`

Match column-I (Solution of salts of salts of...) with column-II (pH of the solution is given by):

Which of the following salts when added to pure water will not alter its `P^(H)`A. Ammonium cyanideB. Ferric chlorideC. Potassium cyanideD. Borax

The hydronium ion concentration in pure water is `1xx10^(-7) ` mol `L^(-1)`. The degree of dissociation of water isA. `1.8 xx 10^(-9)`B. `0.8 xx 10^(-8)`C. `9.8 xx 10^(-6)`D. `3xx10^(-9)`

Our of `HClO_(4)` and `H_(2)SO_(4)`, which is a stronger acid in an aqueous solutionA. `HClO_(4)`B. `H_(2)SO_(4)`C. Both are equally strongD. Strength depends on concentration

The pH of the solutions produced by mixing equal volumes of `2.0 xx 10^(-3) M HClO_(4)` and `1.0 xx 10^(-2) MKClO_(4)` isA. 2.7B. 2.3C. `3.0`D. `1.0`

Which of the following salts will not undergo hydrolysis in water?A. Sodium sulphateB. Ammonium sulphateC. Aluminimum sulphateD. All the salts will hydrolyse

Which of the following salts will not change the `pH` of pure water on dissociation?A. `KCI`B. `AICI_(3)`C. `Na_(2)CO_(3)`D. `AI_(2)(SO_(4))_(3)`

The following equilibrium is established when `HC1O_(4)` is dissolved in weak acid `HF`, `HF+HClO_(4)hArrClO_(4)^(-)+H_(2)F^(+)` Which of the following is correct set of conjugate acid base pair?A. `HF` and `HCIO_(4)`B. `HF` and `CIO_(4)^(-)`C. `HF` and `H_(2)F`D. `HCIO_(4)` &`H_(2)F^(+)`

In the following reaction `HC_(2)O_(4)^(-)(aq)+PO_(4)^(3-)(aq)hArrHPO_(4)^(-2)(aq)+C_(2)O_(4)^(2-)(aq)`, which are the two Bronsted bases?A. `HC_(2)O_(4)^(-)` and `PO_(4)^(3-)`B. `HPO_(4)^(2-)` and `C_(2)O_(4)^(2-)`C. `PO_(4)^(3-)` and `C_(2)O_(4)^(2-)`D. `HC_(2)O_(4)^(-)` and `HPO_(4)^(2-)`

The solubility of `CaCO_(3)` is `7mg//L`. Calculate the `K_(sp)` of `BaCO_(3)` whne `Na_(2)CO_(3)` is added slowely a solution containing equimolar concentration of `Ca^(2+)` and `Ba^(2+)` and no precipitate is formed until `90%` of `Ba^(2+)` has beem precipitated as `BaCO_(3)`.

To separate and identify the ionis in a mixutre that may contain `Pb^(2+), Cu^(2+)` and `Mg^(2+)` use the reagents `H_(2)S, HCI` and NaOH. They should be added in the order:A. `HCI, H_(2)S, NaOH`B. `H_(2)S, HCI, NaOH`C. `HCI, NaOH, H_(2)S`D. `NaOH, H_(2)S, HCI`

Among the mixutre (i) `50 ml` of `N//10 HCl + 50 ml` of `N//10 NaOH` (ii) `55 ml` of `N//10 HCl + 45 ml` of `N//10 NaOH` (iii) `75 ml` of `N//10 HCl + 25 ml` of `N//10 NaOH` (iv) `30 ml` of `N//5 HCl + 70 ml` of `N//5 NaOH` For how many of the above mixutres pH lies between 1 to 7

The ionisation constant of dimethylamine is `5.4xx10^(-4)`. Calculate its degree of ionization in its `0.02M` solution. What percentage of dimethylamine is ionized if the solution is also `0.1 M` in `NaOH`?