BCH102
1. Calculate the molarity of a solution prepared by dissolving 11.7 g NaCl in enough water to make 500 mL
of solution.
Molar mass of NaCl = 58.5 g/mol.
2. How many grams of Na2CO3 are required to prepare 250 mL of 0.40 M Na2CO3 solution?
Molar mass of Na2CO3 = 106 g/mol.
3. What volume of 2.0 M HCl is required to prepare 500 mL of 0.25 M HCl?
4. For the reaction: N2(g) + 3H2(g) ⇌ 2NH3(g)
At 500°C, Kc = 6.0 × 10^-2. Calculate Kp. Given:
Kp = Kc(RT)^Δn R = 0.0821 L·atm·mol^-1·K^-1
5. How many grams of NaCl are required to prepare 500 mL of 0.20 M NaCl?
Molar mass of NaCl = 58.5 g/mol. (2)
6. How much 2.0 M HCl is required to prepare 250 mL of 0.40 M HCl? (2)
7. For the reaction:
2SO2(g) + O2(g) ⇌ 2SO3(g)
At equilibrium:
[SO₂ ] = 0.40 M
[O₂ ] = 0.20 M
[SO₃ ] = 0.60 M
a) Write the expression for Kc. (1)
b) Calculate Kc. (2)
8. Calculate the pH of a buffer containing 0.20 M CH3COOH and 0.30 M CH3COONa. Given: pKa = 4.75.
(3)
9. A reaction is very slow at room temperature. After adding a catalyst, the reaction becomes much faster.
a) What happens to the activation energy? (1)
b) Does the catalyst change the equilibrium position? (1)
c) Explain why the reaction becomes faster even though the catalyst does not change the equilibrium
position. (1)
10. A buffer contains 0.25 M NH3 and 0.40 M NH4Cl.
Calculate its pH.
Given:
Kb for NH3 = 1.8 × 10^-5