Tag: chemical equilibrium and acids-bases

Questions Related to chemical equilibrium and acids-bases

An aqueous solution of a salt of a weak base and a strong acid is acidic because of:

chemistry water drying and dehydrating agents hydrolysis of salts and the ph of their solutions chemical equilibrium and acids-bases

  1. electrolysis

  2. hydrolysis

  3. dissociation

  4. none of the above

Show answer
Correct Option: B
Explanation:

A salt of strong acid and weak base undergo hydrolysis on action with water and flourishes $H^{+}$ ion due to hydrolysis of cation. Hence, an aqueous solution of a salt of a weak base and a strong acid is acidic.

Which of the following salts can produce only two types of radicals?

chemistry water drying and dehydrating agents hydrolysis of salts and the ph of their solutions chemical equilibrium and acids-bases

  1. $NaKCO _3$

  2. $CaOCl _2$

  3. $NH _4HSO _4$

  4. $Na(NH _4)HPO _4$

Show answer
Correct Option: C
Explanation:

$NaKCO _3\rightarrow Na^++K^++CO _{3}^{-2}$
$CaOCl _2\rightarrow Ca^{+2}+OCl^-+Cl^-$
$NH _4HSO _4\rightarrow NH _{4}^{+}+HSO _{4}^{-}$
(2 types of radicals)
$Na(NH _4)HPO _4\rightarrow Na^++NH _{4}^{+}+HPO _{4}^{-}$

The hydrated salt $Na _{2}SO _{4}, 10H _{2}O$ undergoes $X\%$ loss in weight on heating and becomes anhydrous. The value of $X$ will be:

chemistry water drying and dehydrating agents hydrolysis of salts and the ph of their solutions chemical equilibrium and acids-bases

  1. $10$

  2. $45$

  3. $56$

  4. $70$

Show answer
Correct Option: C
Explanation:

Molecular mass of $Na _2SO _410H _2O=2\times23+32+16\times14+1\times20=322$


On heating the $Na _2SO _410H _2O$ it becomes anhydrous that means 10 $H _2O$ molecules separated

Molecular mass of $10H _2O=20\times1+10\times16=180$

% loss $=\dfrac{180}{322}\times100=55.9$ % $ =56$ %

Which of the following salts will have maximum cooling effect when $0.5$ mole of the salt is dissolved in same amount of water. Integral heat of solution at $298\ K$ is given for each salt.

chemistry water drying and dehydrating agents hydrolysis of salts and the ph of their solutions chemical equilibrium and acids-bases

  1. $KNO _{3}  (\Delta =35.4\ kJ\ mol^{-1})$

  2. $NaCl  (\Delta =5.35\ kJ\ mol^{-1})$

  3. $HBr  (\Delta =83.3\ kJ\ mol^{-1})$

  4. $KOH  (\Delta =55.6\ kJ\ mol^{-1})$

Show answer
Correct Option: A
Explanation:

More the heat absorbed, more will be the cooling effect. Hence more the positive value of $\Delta H$ more the cooling effect.In the given question KBr has $\Delta H =83.3 kJmol^-$ which is highest among all the gases.

The compound whose $0.1\space M$ solution is acidic:

chemistry water drying and dehydrating agents hydrolysis of salts and the ph of their solutions chemical equilibrium and acids-bases

  1. Ammonium formate

  2. Ammonium sulphate

  3. Ammonium chloride

  4. Sodium formate

Show answer
Correct Option: B,C
Explanation:

Concept :-

  A compound will be acidic if it form strong acidic solution after dissolving in water.
A. $HCOONH _4 + H _2 O \rightarrow \underset{Weak \, acid}{HCOOH} + \underset{weak \, base}{NH _4OH}$

B. $(NH _4) _2 SO _4 + 2H _2 O \rightarrow \rightarrow \underset{Strong \, acid}{H _2SO _4} + \underset{Weak\, base}{2NH _4OH}$

C. $NH _4 Cl + H _2O \rightarrow \underset{Weak \, base}{NH _4 OH} + \underset{Strong \, acid}{HCl}$

D. $HCO\overset{-}{O}N\overset{+}{a} + H _2O \rightarrow \underset{Strong \, base}{NaOH} + \underset{Weak \ acid}{HCOOH}$

During the preparation of hydrogen chloride gas on a humid day, the gas is usually passed through two guard tube containing calcium chloride. The role of calcium chloride in the guard tube is:

chemistry water drying and dehydrating agents hydrolysis of salts and the ph of their solutions chemical equilibrium and acids-bases

  1. it absorbs the evolved gas

  2. it moisten the gas

  3. it absorbs moisture from the gas

  4. it absorbs $Cl^-$ ions form the gas evolved

Show answer
Correct Option: C
Explanation:

Calcium chloride is hygroscopic in nature and its anhydrous salt is deliquescent and it can accumulate enough water in its crystal lattice to form a solution. It is used as a drying agent to absorb moisture from the environment.

$MgC{l} _{2}$ and $NaCl$ are both salts that are used to treat roads. Which salt will have the greatest effect on the freezing point and why?

chemistry water drying and dehydrating agents hydrolysis of salts and the ph of their solutions chemical equilibrium and acids-bases

  1. NaCl because i = 2

  2. MgCl2 because i = 3

  3. MgCl2 because i = 2

  4. NaCl because i = 3

  5. Both salts would have the same effect

Show answer
Correct Option: B
Explanation:

Addition of salt on roads is used to melt the ice, as this causes the lowering of the freezing point of the ice. Hence, freezing point of the ice due to the addition of the salt decreases the freezing point lesser than the $0^oC$.
Which can not be obtained easily , hence ice melts.
Now , as per formula
$ \Delta T _f = i k _f m$
Here , $i = $Vant Hoff's Factor.
which depends upon the number of dissociated ions, more the ions are dissociated from a single formula unit, more will be value of the $i$.
and $i \propto \Delta T _f$
hence , this means higher the value of $i$ , more will be lowering of the freezing point.
So here the (B) $MgCl _2$ is used , which has $i = 3$.

A sodium salt on treatment with ${MgCl} _{2}$ gives white precipitate only on heating. The anion of the sodium salt is:

chemistry water drying and dehydrating agents hydrolysis of salts and the ph of their solutions chemical equilibrium and acids-bases

  1. $ { HCO } _{ 3 }^{ - }$

  2. $ { CO } _{ 3 }^{ 2- }$

  3. $ { NO } _{ 3 }^{ - }$

  4. $ { SO} _{ 4 }^{ 2- }$

Show answer
Correct Option: A
Explanation:
The salt will be sodium bicarbonate and the anion is $HC{ O } _{ 3 }^{ \ominus  }$
When sodium bicarbonate react with $Mg{ Cl } _{ 2 }$ it produce Magnesium bicarbonate which is also soluble in water
But, on heating $Mg{ \left( HC{ O } _{ 3 } \right)  } _{ 2 }$ it produce $Mg\left( C{ O } _{ 3 } \right) $ which gives white precipitate
$Mg{ \left( HC{ O } _{ 3 } \right)  } _{ 2 }\rightarrow Mg\left( C{ O } _{ 3 } \right)+C{ O } _{ 2 }+{ H } _{ 2 }O$

The relative strength of two weak bases at same concentration may be given as:

chemistry chemical equilibrium and acids-bases dissociation constants ionisation of weak acids and weak bases ionization constants of weak acids and weak bases

  1. $\cfrac { { K } _{ { b } _{ 1 } } }{ { K } _{ { b } _{ 2 } } } $

  2. $\cfrac { { \left[ { OH }^{ - } \right] } _{ 1 } }{ { \left[ { OH }^{ - } \right] } _{ 2 } } $

  3. $\cfrac { { \alpha } _{ 1 } }{ { \alpha } _{ 2 } } $

  4. $\cfrac { \sqrt { { K } _{ { b } _{ 1 } } } }{ \sqrt { { K } _{ { b } _{ 2 } } } } $

Show answer
Correct Option: B,C,D
Explanation:

Relative strength of two bases are measured by their degree of dissociation.

For weak base $[OH^-]=C\alpha$ and $K _b=C\alpha^2$
So relative strength of two weak bases at same concentration may be given as $\cfrac{[OH^-] _1}{[OH^-] _2}=\cfrac{C\alpha _1}{C\alpha _2}=\cfrac{\sqrt K _{b1}}{\sqrt K _{b2}}$

What will be the effect of adding $100 ml$ of $0.001 M - HCl$ solution to $100 ml$ of a solution having $0.1 M - HA$? The acid dissociation constant of $HA$ is $10^{-5}$.

chemistry chemical equilibrium and acids-bases dissociation constants ionisation of weak acids and weak bases ionization constants of weak acids and weak bases

  1. The degree of dissociation of $HA$ will decrease but the $pH$ of solution remains unchanged.

  2. The degree of dissociation of $HA$ remains unchanged but the $pH$ of solution decreases.

  3. Neither degree of dissociation nor $pH$ of solution will change.

  4. The degree of dissociation as well as $pH$ of solution will decrease.

Show answer
Correct Option: C