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901.

0.02 M monobasic acid dissociates 2% hence, pH of the solution isA. 0.3979B. 1.3979C. 1.699D. 3.3979

Answer» Correct Answer - D
`[H^(+)] = alpha.C = (2)/(100) xx 0.2, [H^(+)] = 4 xx 10^(-4)M`
`pH = -log [H^(+)] = 4 -log 4 , pH = 33979`.
902.

pH of a solution is 9.5. The solution isA. NeutralB. AcidicC. BasicD. Amphoteric

Answer» Correct Answer - C
When pH = 7 means neutral, `pH lt 7` means acidic, `pH gt 7` means basic.
903.

Which on reaction with water will have pH less than 7A. BaOB. CaOC. `Na_(2)O`D. `P_(2)O_(5)`

Answer» Correct Answer - D
`BaO, CaO` and `Na_(2)O` are shows more than 7 pH because of their basic nature.
904.

Which of the following will decrease the pH of a 50 ml solution of `0.01 M HCI` ?A. Addition of 50 mL of 0.01 M HClB. Addition of 50 mL of 0.02 M HClC. Addition of 150 mL of 0.02 M HClD. Addition of 5 mL of 1 M HCl

Answer» Correct Answer - D
For 0.01 M HCl, `|H^(+)| =10^(-2), pH=2`
`(A) N_(1)V_(1)+N_(2)V_(2)=N_(3)(V_(1)+V_(2))`
`50 xx 0.01+50 xx 0.01 =N_(3)(50+50)`
or `N_(3)=(.5 +.5)/(100)=10^(-2),pH=2` (No change)
`(B) 50 xx 0.01 +c0 xx 0.002=N_(3)(50+50)`
or `N_(3) =(0.5 +0.1 )/(100)=6 xx 10^(-3)`
`pH= - log (6 xx 10^(-3))=2.22 (`pH increases)
`(C ) 50 xx 0.01 +150 xx 0.002 = N_(3)(50+150)`
or `N_(3)=(.5 +.3)/(200)=4 xx 10^(-3)`
`pH =-log (4 xx 10^(-3))=2.39 pH (pH ` increases )
`(D) 50 xx 0.01 +5 xx 1 =N_(3)(50+5)`
or `N_(3)=(0.5 +5)/(55)=(5.5)/(5)=10^(-1)`
`pH =1 (`pH decreases )
905.

Which would be decrease the pH of `25 cm^(3)` of a 0.01 M solution of hydrochloric acidA. The addition of `25cm^(3)` 0.005 M hydrochloric acidB. The addition of `25cm^(3)` of 0.02 M hydrochloric acidC. The addition of magnesium metalD. None of these

Answer» Correct Answer - B
Given concentration of HCl = 0.01 M
`pH = -log 10^(-2) = 2`
In option (b)
Concentration of HCl = 0.02 M
M.eq `= 0.02 xx 25 = .5 M`. Eq of HCl
M.eq in given condition `= 0.01 xx 25 = 0.25`
Total M.eq in solution `= 0.25 + 0.50 = 0.75 = (.75)/(25+25) = 1.5 xx 10^(-2)N`
Then new pH will be
`= -log 1.5 xx 10^(-2) = 2 - log 1.5`
Which is less than 2 ltbr. So we canvery that that by adding `25cm^(3)` of 0.2 M HCl the pH of `25 cm^(3)` of 0.01 M decrease.
906.

Which one of the following is not a buffer solutionA. `0.8 M H_(2)S + 0.8 M KHS`B. `2M C_(6)H_(5)NH_(2) + 2M C_(6)H_(5)overset(+)(N)H_(3)Br`C. `3M H_(2)CO_(3) + 3M KHCO_(3)`D. `0.05 M KClO_(4) + 0.05 M HClO_(4)`

Answer» Correct Answer - D
907.

The mixture of `10 ml 0.5 N CH_(3)COOH` and `10 ml 0.25 M NaOH`, having `pH = 5`, then find the value of pKa?

Answer» Correct Answer - 5
908.

Which can act as bufferA. `NH_(4)Cl + HCl`B. `CH_(3)COOH + H_(2)CO_(3)`C. `40mL` of `0.1M NaCN + 20mL` of `0.1M HCN`D. `NaCl + NaOH`

Answer» Correct Answer - C
Acidic buffer is a weak acid and its salt of strong base
909.

Assertion (A): The `pH` of an aqueous solution of `CH_(3)COOH` remains unchanged on the addition of `CH_(3)COONa`. Reason (R) : The `pH` of an aqueous solution of `CH_(3)COOH` remains unchanged on the addition of `CH_(3)COONa`. Reason (R) : The ionisation of `CH_(3)COOH` is supressed by the addition of `CH_(3)COONa`.A. If both (A) and (R) are correc, and (R) is the correct explanation of (A).B. If both (A) and (R) are correct but (R) is not the correct explanation of (A).C. If (A) is correct, but (R) is incorrect.D. If (A) is incorrect, but (R) is correct.

Answer» Correct Answer - D
`(A)` is wrong. It forms acidic buffer and this `pH` changes. `(R)` is correct. Due to common ion `(CH_(3)COO^(Theta))`, ionisation of `CH_(3)COOH` is supressed.
910.

When `CH_(3)COONa` is added to an aqueous solution of `CH_(3)COOH`A. The pH of solution decreasesB. The pH of solution increasesC. The pH of the solution remains unalteredD. An acid salt is produced

Answer» Correct Answer - B
`P^(H) = P^(Ka) + "log" (["salt"])/(["acid"])`
911.

The `[H^(+)]` in `0.2M` solution of formic acid is `6.4xx10^(-3)` mol `litre^(-1)`. To this solution formate is added so as to adjusrt the conc.of sodium formate to one mol per litre. What will be pH of this solution ? `(K_(a) for HCOOH=2.4xx10^(-4))` and degree of dissociation of `HCOONa = 0.75`)

Answer» In `0.2M HCOOH, [H^(+)]= 6.4xx10^(-3)`
`Calpha= 6.4xx10^(-3)`
`:. alpha= 3.2xx10^(-2)`
Now sodium formate is added and the dissociation will fiurther be suppressed and therefore, new degree of dissociation `(alpha_(1))` for HCOOH in presence of HCOONa is so small that it may be neglected.
`:. [HCOOH]` after dissociation
= [HCOOH] before dissociation
`[HCOOH]= 0.2`
`{:(,HCOONahArr,HCOO^(-)+,Na^(+)),("Conc. before dissociation", 1,0,0),("Conc. after dissociartion", (1-0.75),0.75,0.75):}`
So `[HCOOH]= 0.2`
`:. [HCOO^(-)]= 0.75`
`pH= -log 2.4xx10^(-4)+log((0.75)/(0.2))=4.19`
912.

The degree of hydrolysis of a salt of `W_(A)` and `W_(B)` in its `0.1M` solution is `50%`. If the molarity of the solution is `0.2M`, the percentage hydrolysis of the salt woukd beA. `25%`B. `50%`C. `75%`D. `100%`

Answer» Correct Answer - B
For the salt of `W_(A)//W_(B)`, the degree of hydrolysis is independent of concentration.
913.

The sodium salt of a certain weak monobasic organic acid is hydrolysed to an extent of 3% in its 0.1 M solution at `25^@C`.Given that the ionic product of water is `10^(-14)` at this temperature , what is the dissociation constant of the acid ?A. `~~1xx10^(-10)`B. `~~1xx10^(-9)`C. `3.33xx10^(-9)`D. `3.33xx10^(-10)`

Answer» `h=0.3 C=0.1M`
`K_(h)=CH^(2)=9xx10^(-5)`
`K_(h)=(K_(w))/(K_(a))=9xx10^(-5)rArr K_(a)=(10^(-14))/(9xx10^(-5))=1.11xx10^(-10)~~1xx10^(-10)`
914.

The degree of hydrrolysis of a salt of weak acid and weak base in its `0.1M` solultion is found to be `50%`. If the molarity of the solution is `0.2M`, the percentage hydrolysis of the salt should be:A. `100%`B. `50%`C. `25%`D. None of these

Answer» the degree of hydrolysis of a salt of weak acid and weak base is independent of concentration of salt solution.
915.

The pH of a solution is 2. If its pH is to be raised to 4, then the `[H^(+)]` of the original solution has to beA. DoubledB. HalvedC. Increased hundred timesD. Decreased hundred times

Answer» Correct Answer - D
If pH of any solution is 2.
Then `[H^(+)] = 10^(-2) M`.
If pH of any solution is just double then pH = 4 and `[H^(+)]` will be `10^(-4)`.
916.

Assuming `100%` ionization in case of strong electrolytes which of the following will have minimum pHA. 0.1 M `NH_(4)Cl`B. 0.1 M `(NH_94))_(2)SO_(4)`C. 0.1M `(NH_(4))_(3)PO_(4)`D. All will have same pH.

Answer» Correct Answer - B
Minimum pH means maximum `[H^(+)]`
`NH_(4)Cl rarr NH_(4)^(+) +Cl^(-)`
`NH_(4)^(+) +H_(2)O hArr NH_(4)OH +H^(+)`
`:. [H^(+)] =0.01 xx K_(h)`
In case of `(NH_(4))_(2)SO_(4)`
`[H^(+)]=0.02 xx K_(h)`
However `(NH_(4))_(3)PO_(4)` will be almost neutral `(pH ~~7)` as it is a salt of a weak acid and a weak base. Thus pH will be minimum (i.e., highest `H^(+)` conc. ) in case of 0.01 M `(NH_(4))_(2)SO_(4)`
917.

pH of one litre solution containing 40gm of `NaOH`A. 2B. 10C. 8D. 14

Answer» Correct Answer - D
`[OH^(-)] = (40)/(40) = 1`
`p^(OH) = 0`
`p^(H) = 14`
918.

During the titration of a weak base with a strong acid, one should use an acid-base indicator that changes colour in the :A. acid rangeB. basic rangeC. buffer rangeD. neutral range

Answer» Correct Answer - A
919.

A solution of `pH = 9` is one thousand times as basic as a solution of pH.A. 4B. 7C. 10D. 6

Answer» Correct Answer - D
For every `10` times dilution `p^(H)` value decreased by one unit
920.

Arrhenius theory is failed to explain the acidic nature ofA. HClB. `HCOOH`C. `H_(2)SO_(4)`D. `CO_(2)`

Answer» Correct Answer - D
Substance that gives `H^(+)` ions when dissolved in water
921.

The pH of solution is `9`. It is `"………"` times more basic than a solution with `pH = 6`A. `3`B. `2`C. `4`D. `6`

Answer» Correct Answer - C
For every ten times dilution `P^(H)` decreased by one unit
922.

The `pH` of a solution increased from `3` to `6`. Its `[H^(o+)]` will beA. Reduced to halfB. DoubledC. Reduced by `1000` timesD. Increased by `1000` times

Answer» Correct Answer - C
If pH is increased by `3` units then strength of the acids decreased by `1000` times
923.

`HCl` gas cannot act as an acid inA. Polar solventsB. Highly polar solventsC. `NH_(3)` liquidD. Non-polar solvents.

Answer» Correct Answer - D
In Non polar solvents `HCl` does not dissociate to give `H^(+)` ions
924.

Which of the following is an Arrhenius acid?A. `CO_(2)`B. `SO_(2)`C. `FeCl_(2)`D. `HNO_(2)`

Answer» Correct Answer - D
`HNO_(3)` produce `H^(+)` ions in water
925.

`0.1 M HCl` solution is diluted by `100` times The pH of the solution formed isA. `3`B. `2`C. `4`D. `6`

Answer» Correct Answer - A
`[H^(+)] = 0.1 xx (1)/(100)`
`= 10^(-3)`
`:. P^(H) = 3`
926.

`100 ml` of a solution of `HCl` with `pH` value `3` is diluted with `400 ml` of water. The new `P^(H)` of the solution isA. `3.7`B. `5.3`C. `4.2`D. `5.6`

Answer» Correct Answer - A
`100 xx 10^(-3) = 500 xx [H^(+)]`
927.

`10^(-6)M HCl` is diluted to `100` times. Its `pH` is:A. 6B. 8C. 6.95D. 9.5

Answer» Correct Answer - c
928.

The weakest base among the followingA. `I^(-)`B. `Cl^(-)`C. `F^(-)`D. `Br^(-)`

Answer» Correct Answer - A
Strong acid conjugate base is the weakest base
929.

Which of the following mixture is not a buffer solutionA. `100 mL` of `0.5 N CH_(3)COOH + 100 mL ` of `0.05 N NaOH`B. `100 mL` of `0.6 N HCN + 100 mL` of `0.4 NaOH`C. `100 mL` of `0.5N NH_(4)OH + 10 mL` of `0.2 NCH_(3)COOH`D. `100 mL` of `0.4 N HCL + 100 mL` of `0.4N NaOH`

Answer» Correct Answer - D
A mixutre of storng acid and strong base does not acts as buffer
930.

Which solutionwill have pH closer to `1.0` ?A. 100 mL of `(M//10) HCI + 100 mL` of `(M//10) NaOH`B. 55 mL of `(M//10) HCI +45 mL` of `(M//10) NaOH`C. 75 mL of `(M//10) HCI + 90` mL of `(M//10) NaOH`D. 75 mL of `(M//5) HCI +25 mL of `(M//5) NaOH`

Answer» Correct Answer - D
931.

The following has no conjugate baseA. `H_(2)PO_(4)^(-)`B. `H_(2)PO_(2)^(-)`C. `H_(2)PO_(3)^(-)`D. `CH_(3)COOH`

Answer» Correct Answer - B
`H_(2)PO_(2)^(-)` has no conjugate base `H-underset(H)underset(|)overset(O)overset(||)P-O^(-)`
932.

Which solutionwill have pH closer to `1.0` ?A. `75 mL` of `M//5HC1 + 25 mL` of `M//5 NaOh`B. `10mL` of `M//10 HC1 + 90 mL` of `M//10 NaOH`C. `55mL` of `M//10 HC1` + `54mL` of `M//10 NaOH`D. `100 mL` of `M//10 HC1 + 100 mL` of `M//10 NaOH`

Answer» Correct Answer - A
a.mmol of `HC1 = 75 xx (1)/(5) = 15`
mmol of `NaOH = 25 xx (1)/(5) = 5`
mmol of HC1 left `= 15 - 5 = 10`
Volume `= 75 + 25 = 100`
`[H^(o+)] = (10)/(100) = 0.1 = 10^(-1)M`
`pH = 1`
b. mmol of `HC1 = 10 xx (1)/(10) = 1`
mmol of `NaOH = 90 xx (1)/(10) = 9`
mmol of `NaOH` left `= 9 - 1 = 8`
Since base is left, `:. pH gt 7`
c. mmol of `HC1 = 55 xx (1)/(10) = 5.5`
mmol of `NaOH = 45 xx (1)/(10) = 4.5`
mmol of `HC1` left `= 5.5 - 4.5 = 1.0`
Volume `= 55 + 45 = 100`
`[H^(o+)] = (1)/(100) = 10^(-2)`
`pH = 2`
d. mmol of `HC1 = 100 xx (1)/(10) = 10`
mmol of `NaOH = 100 xx (1)/(10) = 10`
Both `S_(A)` and `S_(B)` are neutralised.
`:. pH = 7`.
933.

Which of the following solution will have `P^(H)` closer to `1.0`?A. `100 ml` of `M//10 HCl +` `45 ml` of `M//10 NaOH`B. `55 ml` of `M//10HCl +``45 ml` of `M//10 NaOH`C. `10 ml` of `M//10 HCl+` `90 ml` of `M//10 NaOH`D. `75ml` of `M//5 HCl+` `25 ml` of `M//5 NaOH`

Answer» Correct Answer - D
`[H^(+)] = (NaVa - NbVb)/(Va + Vb)` (if `NaVa gt NbVb`)
`P^(H) = -"log"^([H^(+)])`
`[H^(+)] = 10^(-1), :. P^(H) = 1`
934.

Weskest base isA. `C_(2)H^(-)`B. `NO_(3^(-))`C. `CN^(-)`D. `HS^(-)`

Answer» Correct Answer - B
Strong acid conjugate base is the weakest base
935.

Strongest Bronsted base isA. `ClO^(-)`B. `ClO_(2)^(-)`C. `ClO_(3)^(-)`D. `ClO_(4)^(-)`

Answer» Correct Answer - A
Weak acid conjugate base is the strongest base
936.

`K_(h)` of salt obtained from strong acid and weak base is `2 xx 10^(-5)`. The `K_(b)` of weak base isA. `2 xx 10^(-19)`B. `5 xx 10^(-10)`C. `2 xx 10^(-10)`D. `5 xx 10^(-9)`

Answer» Correct Answer - B
`K_(h) = (K_(w))/(K_(b))`
937.

Which of the following is not a salt?A. `NaCl`B. `Ca(OH)_(2)`C. `PbS`D. `Zn(NO_(3))_(2)`

Answer» Correct Answer - B
`Ca(OH)_(2)` is a base
938.

When `100 ML` of `1.0 M HCl` was mixed `100 MI` of `1.0 M NaOH` in an insulated beakertat constant pressure, a temperature incease of `5.7^(0)C` was measured for the beaker and its contents (Expt.1) Because th enthalpy of neutralization of a c `5.7^(0)C` strong acid with a strong base is constant `(-57.0 kJ moL- I)`, this experiment could be used to measure the calorimeter constant. In a second experiment (Expt.2) , `100 ML` of `2.0 M` acetic acid `(K_(a) =2.0 xx 10^(-5))` was mixed with `100 ML` of `1.0 m NaOH` (under identical conditions to Expt. 1) Where a temperature rise of `5.0^(0)C` was measured. (Consider heat capcity of all solution as `4.2 Jg^(-1)` and density of all solution as `1.0 gmL^(-1)`) Enthalpy of dissociation (in `KJ Mol^(-1)`) of acetic acid obtained from Expt, `2` isA. `1.0`B. `10.0`C. `24.5`D. `51.4`

Answer» Correct Answer - A
939.

When `100 ML` of `1.0 M HCl` was mixed `100 MI` of `1.0 M NaOH` in an insulated beakertat constant pressure, a temperature incease of `5.7^(0)C` was measured for the beaker and its contents (Expt.1) Because th enthalpy of neutralization of a c `5.7^(0)C` strong acid with a strong base is constant `(-57.0 kJ moL- I)`, this experiment could be used to measure the calorimeter constant. In a second experiment (Expt.2) , `100 ML` of `2.0 M` acetic acid `(K_(a) =2.0 xx 10^(-5))` was mixed with `100 ML` of `1.0 m NaOH` (under identical conditions to Expt. 1) Where a temperature rise of `5.0^(0)C` was measured. (Consider heat capcity of all solution as `4.2 Jg^(-1)` and density of all solution as `1.0 gmL^(-1)`) The `p^(H)` of the solution after Expt.2 isA. `2.8`B. `4.7`C. `5.0`D. `7.0`

Answer» Correct Answer - B
940.

Aqueous solution of which of the following shows lower `p^(H)`?A. `KNO_(3)`B. `ZnCl_(2)`C. `CH_(3)COONa`D. `CH_(3)COONH_(4)`

Answer» Correct Answer - B
Cationic hydrolysis
941.

What will the pH of the solution of the salt of weak acid and weak base? `(K_(b) = 1 xx 10^(-6)` and `K_(a) = 1 xx 10^(-4)`)

Answer» Correct Answer - 6
`pH = 1/2 (14 + pK_(a) - pK_(b))`
`(1)/(2)(14+4-6) = 6`
942.

The solubility of a salt of weak acid (AB) at pH 3 is `Y xx 10^(-3) mol L^(-1)`. The value of Y is ___________ (Given that the value of solubility product of `AB(K_(sp)) = 2 xx 10^(-10)` and the value of ionization constant of `HB(K_(a)) = 1 xx 10^(-8))`

Answer» Correct Answer - 4.47
`S = sqrt(K_(sp)(([H^(+)])/(K_(a))+1)) = sqrt(2 xx10^(-10)((10^(-3))/(10^(-8))+1)) = sqrt(2 xx 10^(-5))`
`= 4.47 xx 10^(-3) M`
943.

Assertion `(A):` Equivalent conductance increase with dilution for an electrolyte solution. Reason `(R):` The number of ions per litre of electrolyte increases with dilution.A. S is correct but E is wrong.B. S is wrong but E is correc.C. Both S and E are correct and E is correct explanation of S.D. Both S and E are correct but E is correct explanation of S.

Answer» Correct Answer - A
It is a fact.
944.

In which ratio of volumes 0.4 M HCl and 0.9 M HCl are to be mixed such that the concentration of the resultant solution becomes 0.7 M ?A. `4:9`B. `2:3`C. `3:2`D. `1:1`

Answer» Correct Answer - B
`0.4 xx 6+0.9 (1000-y)=0.7 xx 1000`
`0.4 y +900-0.9 y =700`
`0.5 y =700 -900= -200`
`0.5 y=200` or `y=400`
The ratio of volumes of 0.4 M HCl and 0.9 M HCl to be mixed to get 0.7 M concentration of the solution is `400 : 600` i.e., `2:3`
945.

The pH of `M//100` NaOH solution is `:`A. 2B. 10C. 6D. 12

Answer» Correct Answer - D
`[OH^(-)]=[NaOH]=10^(-2)M`
`[H^(+)]=(K_(w))/([OH^(-)])=(10^(-14))/(10^(-2))=10^(-12)`
`pH=2`
946.

A certain buffer solution sontains equal concentration of `X^(-)` and `HX`. The `K_(a)` for `HX` is `10^(-8)`. The of the buffer isA. 3B. 4C. 11D. 14

Answer» Correct Answer - B
`pH=pK_(a)+log.(["Salt"])/(["Acid"])`
`=-log (1.0 xx 10^(-8)) +log. (0.1)/(0.1)`
`-log 10^(-8) +0=8`
947.

A certain weak acid has a dissociation constant of `1.0 xx 10^(-4)`. The equilibrium constant for its reaction with a strong base isA. `1.0 xx 10^(-4)`B. `1.0 xx 10^(-10)`C. `1.0 xx 10^(10)`D. `1.0 xx 10^(14)`

Answer» Correct Answer - C
The equilibrium constant for the neutralization of a weak acid with a strong base,
`K = (K_(a))/(K_(w)) = (1.0 xx 10^(-4))/(1.0 xx 10^(-14)) = 1.0 xx 10^(10)`
948.

A certain buffer solutions contains equal concentration of `X^(-)` and HX. The `K_(b)` for HX is `10^(-10)`. The pH of the buffer isA. 4B. 7C. 10D. 14

Answer» Correct Answer - A
`X^(-) + H_(2)O hArr OH^(-) + HX`
`K_(b) = ([OH^(-)][HX])/([X^(-)])`
`HX hArr H^(+) + X^(-)`
`K_(a) = ([H^(+)][X^(-)])/([HX]), :. K_(a) xx K_(b) = [H^(+)][OH^(-)] = K_(w) = 10^(-14)`
Hence `K_(a) = 10^(-4)`
Now as `[X^(-)] = [HX], pH = pK_(a) = 4`.
949.

Calculate the volume of water required to dissolve`0.1g` lead (II) chloride to get a saturaed solution `(K_(sp)` of `PbCI_(2) = 3.2 xx 10^(-8)`, atomic mass of `Pb = 207 u)`. Multiply your answer with 10 to get answer.

Answer» Correct Answer - `0002`
950.

0.023 g of sodium metal is reacted with 100`cm^(3)` of water. The pH of the resulting solution isA. 10B. 11C. 9D. 12

Answer» Correct Answer - D
`Na+H_(2)O rarr NaOH +(1)/(2) H_(2)`
1 mol of Na produces 1 mole of NaOH
0.023 g Na`=(0.023)/(23)=10^(-3) ` mole
`:. ` NaOH produced `10^(-3)` mole
`:. |NaOH |=(10^(-3))/(100)xx 1000=10^(-2)M`
`pOH =2` or `pH =14-2 =12`