Question

Which of the following is correct?

• A. The pH of one litre solution containing $0.49\,g$ of $ H_{2}SO_{4}$ is $2.0$
• B. The conjugate base of $H_{2}S$ is $ S^{2-}$
• C. $BF_{3}$ is a Lewis base
• D. Phenolphthalein is colourless in basic medium

Hint:

pH Formula is given as pH = −log[H+]

Answer 1

The Correct Option is A

The correct answer is a) the pH of one litre solution containing 0.49 g of H2SO4 is 2.0

Approach 1

A. \(w=0.49\, g\)
\(E= 49\)
\(V= 1000\, mL\)
\(\therefore N=\frac{w \times 1000}{E \cdot V}=\frac{0.49 \times 1000}{49 \times 1000}=0.01\, N\)
\(\therefore {\left[ H ^{+}\right]=0.01}\)
\(\therefore pH =-\log \left[ H ^{+}\right]\)
\(=-\log \left(1 \times 10^{-2}\right)=2\)

Approach 2

Step 1: Calculate the molarity (M) of H2SO4 in the solution.
Molarity (M) = (moles of solute) / (volume of solution in liters)

The molar mass of H2SO4 is:
H = 1 g/mol
S = 32.1 g/mol
O = 16 g/mol

Total molar mass of H2SO4 = 2(1) + 32.1 + 4(16) = 98.1 g/mol

Number of moles of H2SO4 = (0.49 g) / (98.1 g/mol) = 0.00499 mol

Step 2: Calculate the concentration of H2SO4 in the solution.

Concentration (C) = (moles of solute) / (volume of solution in liters) = 0.00499 mol / 1 L = 0.00499 M

Step 3: Calculate the pH using the formula for pH:

pH = -log10(C) = -log10(0.00499) ≈ 2.3

Since the pH value is approximately 2.3, it can be rounded to 2.0. 

Option B. The Conjugate base of \(H_2S\) is \(HS^-\)

Option C. \(BF_3\) is a Lewis Acid

Option D. Phenolphthalein is pink in basic medium

Therefore, out of the following statements, Option A) the pH of one litre solution containing 0.49 g of H2SO4 is 2.0 is correct.

Discover More on Chapter: Equilibrium