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301.

Which one of the following can be used as an acid base indicator by a visually impared student ?A. LitmusB. TurmericC. Vanilla essenceD. Petunia leaves

Answer» Correct Answer - C
Vanilla essence is an olfactory indicator.
Discussion
302.

`{:(,"Column A",,,"Column B"),(A.,"Methyl orange",(),a.,"Red"),(B.,"Phenolphthalein",(),b.,"Yellow"),(C.,"Turmeric",(),c.,"Colourless"),(D.,"Litmus",(),d.,"Blue"),(,,(),e.,"Pink"):}`

Answer» Correct Answer - `A rarr e`
`B rarr c`
`C rarr b`
`D rarr a`
A `rarr` e Methyl orange shown pink colour in acidic solution.
B `rarr` c Phenolpthalein is colourless in acidic solution.
C `rarr` b Turmeric shows yellow colour in acidic solution.
D `rarr` a Litmus when added to acidic solution gives red colour.
Discussion
303.

Which of the following phenomena occur , when a small amount of acid is added to water? (i) Ionisation ,(ii) Neutralisation ,(iii) Dilution, (iv) FormationA. (i) and (ii)B. (i) and (iii)C. (ii) and (iii)D. (ii) and (iv)

Answer» Correct Answer - B
(i) When water is added to an acid atheri molecules dissociate to from inons
`HCI+H_(2)OrarrH^(+)+CI^(-)+H_(2)O`
`H_(2)O+H^(+)rarrH_(3)O^(+)`(Hydronium ion)
(ii) Mixing of an acid with water is called diultion, it results in the dicrease in the concentration of ions , `(H_(3)O^(+))` per unit volume.
Discussion
304.

The indicator that shows colour changes in the entire pH range isA. phenolphthaleinB. methyl orangeC. universal indicatorD. thymol blue

Answer» Correct Answer - C
Discussion
305.

At a certain temperature, `K_(w)` was found to be `1 xx 10^(-10) mol^(2)//L^(2)`. At this temperature, a solution is taken and red litmus is added to this solution. The solution turned to blue. pH range of the solution could beA. between 5 and 7B. between 7 and 10C. less than 5D. both 1 and 2

Answer» Correct Answer - D
Discussion
306.

According to Lewis theory, neutralisation is theA. transfer of proton from acid to baseB. transfer of proton from base to acidC. transfer of electron pair from acid to baseD. transfer of electron pair from base to acid

Answer» Correct Answer - D
Discussion
307.

Which of the following indicators is the best indicator for the detection of end point in the titration of `CH_(3)COOH` and KOH ?A. methyl organgeB. phenolphthaleinC. methyl redD. none of these

Answer» Correct Answer - B
Discussion
308.

How many moles of NaOH must be added to 200 mL of 0.1 M solution of `HNO_(3)` to get a solution having pH value 2.00 ?

Answer» (i) pH of initial solution
(ii) calculation of normality of the solution after neutralisation
(iii) calculation of number of equivalent of `HNO_(3)` neutralised
(iv) calculation of number of moles of NaOH required to neutralise this `HNO_(3)` in 200 ml
(v) 0.018
Discussion
309.

Assertion (A): Pure nitric acid on standing for long turns yellow. Reason (R): `HNO_(3)` undergoes decomposition and forms `NO_(2)`.A. Both A and R are true and R is correct explanation for A.B. Both A and R are true but R is not the correct for A.C. A is true and R is false.D. A is false and R is true.

Answer» Correct Answer - A
Pure nitric acid on standing for long turns yellow due to its decomposition and the formation of NO_(2), NO_(2)` imparts yellow colour.
Discussion
310.

(1) By using moist blue litmus paper classify the following compounds given below as acids and bases `Ca(OH)_(2), H_(2)SO_(4), CH_(3)COOH, NaOH, KOH, Mg(OH)_(2), HNO_(3), NH_(4)OH` (2) Mention the acidic or basic or neutral nature of solutions by using (a) litmus (b) methyl orange (c) phenolphthalein indicators.

Answer» (a) `{:("Compounds","Colour of blue litmus","Nature of substance"),(Ca(OH)_(2),"No changes","basic"),(H_(2)SO_(4),"change to red","acidic"),(CH_(3)COOH,"change to red","acidic"),(NaOH,"no change","basic"),(KOH,"no change","basic"),("Mg"(OH)_(2),"no change","basic"),(HNO_(3),"change to red","acidic"),(NH_(4)OH,"no change","basic"):}` ltBrgt (b) `{:("Indicators","Acidic","Basic","Neutral"),("Litmus","Red","Blue","No change in colour"),("Methyl orange","Yellow","Pink","No change"),("Phenolphthalein","Colourless","Pink","No change"):}`
Discussion
311.

10 mL of 1 N HCl, 25 mL of 2 N `H_(2)SO_(4)` and 40 mL of X N `HNO_(3)` are mixed and made up to 2000 mL. 100 mL of this solution required 30 mL of NaOH taken from a solution containing 4 g of NaOH in 250 mL of solution. What is the value of X ?

Answer» Normality of NaOH
`N_(1) = (4)/(10) xx (1000)/(250)`
`N_(1) = 0.4 N`
`:. N_(1) V_(1) = N_("mix") V_("mix")`
`0.4 xx 30 = N_("mix") xx 100`
`N_("mix") = 0.12 N`
`((10 xx 1) + (25 xx 2) + (40 xx x))/(2000) = 0.12 N`
`240 = 60 + 40x`
`180 = 40x`
`x = (180)/(40) = 4.5`
`N_(HNO_(3)) = 4.5 N`
Discussion
312.

Calculate the resultant pH of a solution when 20 mL 0.1 N NaOH is mixed with 20 mL of 0.05 M `Ca(OH)_(2) " at " 25^(@)C`

Answer» (i) calculation of net `H^(+)` ion concentration in the mixture
(ii) calculation of the total number of `OH^(-)` ions generated from the given volume of NaOH and `Ca(OH)_(2)`
(iii) calculation of concentrationof `OH^(-)` ions in the resultant solution
(iv) calculation of pOH
(v) calculation of pH from the value of pOH at `25^(@)C`
(vi) 3
Discussion
313.

"X" is a base which is soluble in water. Then the metal present in "X" may beA. aluminumB. copperC. magnesiumD. manganese

Answer» Correct Answer - C
As X is soluble in water. X is alkaline. Generally, metals present in alkalies are Na, K, Mg and Ca.
Discussion
314.

Which among the following is used to remove moisture from the surroundings?A. Calcium chlorideB. Magnesium chlorideC. Zinc chlorideD. Calcium oxide

Answer» Correct Answer - D
Calcium oxide is a hygroscopic substance and hence it is used to remove moisture from the surroundings.
Discussion
315.

Weak acid among the following isA. sulphuric acidB. hydrochloric acidC. nitric acidD. carbonic acid

Answer» Correct Answer - D
Carbonic acid is a weak acid.
Discussion
316.

Which among the following is a weak acid?A. Sulphuric acidB. Hydrochloric acidC. Nitric acidD. Carbonic acid

Answer» Correct Answer - D
Carbonic acid is a weak acid.
Discussion
317.

X is a base which is soluble in water. Then the metal present in X may beA. aluminium.B. copperC. sodiumD. manganese

Answer» Correct Answer - C
As X is soluble in water, X is an alkali. Hence the base is NaOH and it contains sodium.
Discussion
318.

Which of the following is a Lewis acid?(A) H3O+ (B) BF3 (C) NF3 (D) OH-E) N≡N

Answer»

BF3  is a Lewis acid.
Discussion
319.

This species is a carbon-based Lewis acid: (A) CH4 (B) HCCl3 (C) CH3+ (D) CH3- (E) CH3

Answer»

 CH3+ is a carbon-based Lewis acid.
Discussion
320.

Which of these is not a Lewis acid? (A) AlCl3 (B) H3O+ (C) FeCl3 (D) SO3 (E) C4H10

Answer»

C4H10  is not a Lewis acid.
Discussion
321.

According to Lewis theory, a base is a substance that can............

Answer»

According to Lewis theory, a base is a substance that can donate a lone pair of electrons.
Discussion
322.

 Which of the following is not a Lewis base? (A) NH3 (B) H-(C) BF3 (D) H2O (E) H3C-

Answer»

BF3 is not a Lewis base.
Discussion
323.

Which of the following is not both a Bronsted-Lowry acid and a Bronsted-Lowry base? (A) HSO-4  (B) H2PO-4  (C) HCO-3 (D) SH-

Answer»

SH- is not both a Bronsted-Lowry acid and a Bronsted-Lowry base.
Discussion
324.

 Which of the following is not a Bronsted-Lowry acid? (A) H2O (B) (CH3)3N (C) NH4+ (D) CH3CO2H (E) HC≡C

Answer»

HC≡ C is not a Bronsted-Lowry acid.
Discussion
325.

According to Bronsted-Lowry theory, an acid is a substance that can..........

Answer»

According to Bronsted-Lowry theory, an acid is a substance that can donate a proton.
Discussion
326.

Which of these is not a true statement? (A) All Lewis bases are also Bronsted-Lowry bases. (B) All Lewis acids contain hydrogen. (C) All Bronsted-Lowry acids contain hydrogen. (D) All Lewis acids are electron deficient. (E) According to the Bronsted-Lowry theory, water is both an acid and a base.

Answer»

All Lewis acids contain hydrogen is not a true statement.
Discussion
327.

Would water be a good conductor of electricity?

Answer»

Pure water is not a good conductor of electricity.
Discussion
328.

What is meant by neutralization? Give two examples from everyday life of the neutralization reaction.

Answer»
  • In neutralization reaction, an acid reacts with a base to form salt and water. 
  • In a neutralisation reaction the acid dissociates to form H+ ions and base dissociates to form OH ions.
  • They combine to form H2O molecules which mixes with the solvent.

Examples in daily life:

  • When people suffer from acidity, they take some antacids to neutralise the acid in their stomach. 
  • If an ant stings us the pain is due to formic acid. It is neutralised by rubbing moist baking soda which is basic in nature.
Discussion
329.

During electrolysis of copper sulphate, if electric current is passed through the electrolytic cell for a long time, what change would be seen at the anode?

Answer»
  • When electricity is passed for a long time through copper sulphate solution, the following reaction is seen at the anode: Anode Reaction: Cu(s) → Cu2+ (aq) + 2e-
  • All the copper atoms will get converted into copper ions and get deposited on the cathode. This process continues till the copper anode exists.
Discussion
330.

State the differences.The Negative electrode and the positive electrode.

Answer»

The Negative electrode and the positive electrode.

Negative ElectrodePositive Electrode
(i) Negatively charged electrodes are called as a cathode.Positively charged electrodes are called as Anode.
(ii) Positively charged cations move towards the cathode or negative electrode.Negatively charged anions move towards the anode or positive electrode.
(iii) Cathode accepts electrons from cationsAnode gives electrons to anions
Discussion
331.

What is universal indicator? Which is the most accurate method of measuring the pH of a solution?

Answer»
  • In the pH scale, the pH of solutions varies from 0 to 14 in accordance with the strength of the acid or base. 
  • To show these variations in pH, a universal indicator is used. 
  • A universal indicator shows different colours at different values of pH. A universal indicator is made by mixing several synthetic indicators in specific proportions. 
  • The pH of a solution can be determined by means of a universal indicator solution or the pH paper made from it. 
  • However, the most accurate method of measuring the pH of a solution is to use an electrical instrument called pH meter.
  • In this method, pH is measured by dipping electrodes into the solution.
Discussion
332.

Obtain a sample of rainwater. Add to it a few drops of universal indicator. Meausre its pH. Describe the nature of the sample of rainwater and explain the effect if it has on the living world.

Answer»
  • pH of rain water is 6.5 that means rain water is slightly acidic. 
  • When we add universal indicator to rain water it turns orangish red, indicating pH value is between 0 to 7, which tells us that rain water is acidic in nature. 
  • Most of the plants grow best when pH of soil is close to 7. If the soil is too acidic or too basic, it affects plant growth.
Discussion
333.

……………. produced in stomach helps in digestion. (a) Hydrochloric acid (b) Oxalic acid (c) Sulphuric acid (d) Nitric acid

Answer»

Correct option is: (a) Hydrochloric acid
Discussion
334.

A dry pellet of a common base B, When kept in open absorbs moisture and turns sticky. The compund is also a by poroduct of chlor alkali process . Identify B, what type of reaction occurs when B is treated with an acidic oxide? Write a blanced chemical eqution for one such solution

Answer» Sodium hydroxide (NaOH) is commonly used base and is hydroscospic , that is , it absorbs moisture from the atmosphere and becomes sticky.
Thus base B is NaOH (sodium hydroxide). It is also a by product of chlor alkali process
The acidic oxide reacts with base to give slat and water
If `CO_(2)` is the acidic oxide taken then the following reaction takes place with B.
`2NaOH+CO_(2)rarrNa_(2)CO_(3)+H_(2)O`
Such rection is called neutralisation reaction
Discussion
335.

`{:(,"Column A",,,"Column B"),(A.,"Carbonic acid",(),a.,"Baking Powder"),(B.,"Tartaric acid",(),b.,"Antacid"),(C.,"Caustic soda",(),c.,"Soft drinks"),(D.,"Milk of magnesia",(),d.,"Additive in food stuffs"),(,,(),e.,"Soap industry"):}`

Answer» Correct Answer - `A rarr c`
`B rarr a`
`C rarr e`
`D rarr b`
A `rarr` c Carbonic acid is used in soda water and soft drinks.
B `rarr` a Tartaric acid is a component of baking powder. Tartaric acid is used in making cakes for baking process.
C `rarr` e Sodium hydroxide is used in soap industry.
D `rarr` b Magnesium hydroxide is used as antacid to neutralise the acidity.
Discussion
336.

Common salt besides being used in kitchen can also be used as the raw meterial for making `(i) "washing soda"" "(ii) "bleaching powder" " "(iii)"baking soda" " "(iv) "slaked lime" `A. (i) and (ii)B. (i), (ii) and (iv)C. (i) and (iii)D. (i) ,(iii) and (iv)

Answer» Correct Answer - C
Common slt (NaCl) is used in the commercial preparation of both washing soda and baking soda.
Discussion
337.

How would yuou distinguish between baking powder and washing soda by heating ?

Answer» On heating `NaHCO_(3)` (baking soda), `CO_(2)` (carbon dioxide) gas is given out that turns lime water milky.
`2NaHCO_(3)overset(Heat)rarrNa_(2)CO_(3)+H_(2)O+cO_(2)uparrow`
While on heating `Na_(2)CO_(3).10H_(2)O`(washing soda) water of crystallisation is given out and the slat becomes anhydrous. The presence of water of crystallisation given as p[roduct can be tested by treating it with anhydrous `CuSO_(4)` (white) which becomes blue in colour in its contact.
`Na_(2)CO_(3).10H_(2)Ooverset(Heat)rarrNa_(2)CO_(3)+10H_(2)O`
Discussion
338.

A solution reacts with crushed egg-shells to give a gas that turns lime-water milky. The solution containsA. NaClB. HClC. LiClD. KCl

Answer» (b) The solution contains HCl.
Discussion