jee main chemistry important questions | Solutions jee main questions FREE

Q 21 :

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R

Assertion A: 3.1500 g of hydrated oxalic acid dissolved in water to make 250.0 mL solution will result in 0.1 M oxalic acid solution.

Reason R: Molar mass of hydrated oxalic acid is 126 g ${mol}^{- 1}$ .

In the light of the above statements, choose the correct answer from the options given below: [2023]

A is true but R is false
Both A and R are true and R is the correct explanation of A
A is false but R is true
Both A and R are true but R is not the correct explanation of A

1

2

3

4

(2)

$Molarity (M) = \frac{wt}{M . wt} \times \frac{1000}{V (mL)}$

$= \frac{3.15}{126} \times \frac{1000}{250} = 0.1$

Reason is correct as it is used as a fact in the explanation of Assertion.

Q 22 :

The density of 3 M solution of NaCl is 1.0 g ${mL}^{- 1}$ . Molality of the solution is ______ $\times 10^{- 2}$ m. (Nearest Integer).

Given: Molar mass of Na and Cl is 23 and 35.5 g ${mol}^{- 1}$ respectively. [2023]

0%

(364)

$Molality (m) = \frac{M \times 1000}{1000 \times d - M \times M_{solute}}$

$= (\frac{3 \times 1000}{1000 \times 1 - 3 \times 58.5})$

$= 3.6386 m$

$= 363.86 \times 10^{- 2} m = 364$

Q 23 :

A 300 mL bottle of soft drink has 0.2 M ${CO}_{2}$ dissolved in it. Assuming ${CO}_{2}$ behaves as an ideal gas, the volume of the dissolved ${CO}_{2}$ at STP is ______ mL. (Nearest Integer)

Given: At STP, molar volume of an ideal gas is 22.7 L ${mol}^{- 1}$ . [2023]

0%

(1362)

${Number of moles of CO}_{2} = M \times V \times 10^{- 3}$

$= 0.2 \times 300 \times 10^{- 3} = 0.06 mole$

${Volume of CO}_{2} (at STP) = 0.06 \times 22.7$

$= 1.362 L = 1362 mL$

Q 24 :

20 mL of calcium hydroxide was consumed when it was reacted with 10 mL of unknown solution of $H_{2} {SO}_{4}$ . Also 20 mL standard solution of 0.5 M HCl containing 2 drops of phenolphthalein was titrated with calcium hydroxide, the mixture showed pink colour when burette displayed the value of 35.5 mL whereas the burette showed 25.5 mL initially.
The concentration of $H_{2} {SO}_{4}$ is ______ M. (Nearest integer) [2023]

0%

(1)

(i) ${Ca(OH)}_{2} + 2 HCl \to {CaCl}_{2} + 2 H_{2} O$

Millimole $M_{1} \times 10 (2 \times M_{1}) 10$

Millimole of HCl = $(2 \times M_{1}) 10 = 0.5 \times 20$

$M_{{Ca(OH)}_{2}} of HCl = 0.5 M$

(ii) With $H_{2} {SO}_{4}$ ${⇒Ca(OH)}_{2} + H_{2} {SO}_{4} \to {CaSO}_{4} + 2 H_{2} O$

$0.5 \times 2 (M_{2} \times 10)$

$M_{2} \times 10 = 0.5 \times 20$

$M_{2} = 1$

${Molarity of H}_{2} {SO}_{4} = 1$

Q 25 :

The number of units, which are used to express concentration of solution from the following is ______. Mass percent, Mole fraction, Molarity, ppm, Molality [2023]

0%

(5)

Mole fraction, molarity, molality, mass % and ppm describes the concentration of solution.

Q 26 :

A solution of sugar is obtained by mixing 200 g of its 25% solution and 500 g of its 40% solution (both by mass). The mass percentage of the resulting sugar solution is ______ (Nearest integer). [2023]

0%

(36)

Total mass of sugar in mixture of 25% of 200 and 40% of 500 g

$Sugar in solution = 0.25 \times 200 + 0.40 \times 500$

$= 50 + 200 = 250 g$

$Total mass of solution = 200 + 500 = 700 g$

$Mass of sugar in solution = \frac{250}{700} \times 100 = 35.7 %$

$\approx 36 %$

Topic Question Set

Q 22 :

The density of 3 M solution of NaCl is 1.0 g ${mL}^{- 1}$ . Molality of the solution is ______ $\times 10^{- 2}$ m. (Nearest Integer).

Given: Molar mass of Na and Cl is 23 and 35.5 g ${mol}^{- 1}$ respectively. [2023]

0%

Q 23 :

A 300 mL bottle of soft drink has 0.2 M ${CO}_{2}$ dissolved in it. Assuming ${CO}_{2}$ behaves as an ideal gas, the volume of the dissolved ${CO}_{2}$ at STP is ______ mL. (Nearest Integer)

Given: At STP, molar volume of an ideal gas is 22.7 L ${mol}^{- 1}$ . [2023]

0%

0%

Q 25 :

The number of units, which are used to express concentration of solution from the following is ______. Mass percent, Mole fraction, Molarity, ppm, Molality [2023]

0%

Q 26 :

A solution of sugar is obtained by mixing 200 g of its 25% solution and 500 g of its 40% solution (both by mass). The mass percentage of the resulting sugar solution is ______ (Nearest integer). [2023]

0%

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