Question
Chemistry Question on Equilibrium
Which of the following is correct?
The pH of one litre solution containing 0.49g of H2SO4 is 2.0
The conjugate base of H2S is S2−
BF3 is a Lewis base
Phenolphthalein is colourless in basic medium
The pH of one litre solution containing 0.49g of H2SO4 is 2.0
Solution
The correct answer is a) the pH of one litre solution containing 0.49 g of H2SO4 is 2.0
Approach 1
A. w=0.49g
E=49
V=1000mL
∴N=E⋅Vw×1000=49×10000.49×1000=0.01N
∴[H+]=0.01
∴pH=−log[H+]
=−log(1×10−2)=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 H2S is HS−
Option C. BF3 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.
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