Question

25 cm^3 of potassium hydroxide solution react with 20 cm^3 of 2 mol/dm^3 sulfuric acid. The chemical equation for the reaction is given below:

[ 2KOH (aq) + H_2SO_4(aq) rightarrow K_2SO_4(aq) + 2H_2O (l) ]

a) Calculate the number of mol of sulfuric acid (2 marks)
b) Calculate the number of mol of KOH which reacted with the number of mol of the acid in (a) (1 mark)
c) Calculate the concentration of KOH in mol/dm^3 (2 marks)
d) Calculate the number of mol of potassium sulfate (K_2SO_4) produced (1 mark)
e) Calculate the mass in grams of potassium sulfate produced (Relative atomic masses: K = 39, S = 32, O = 16). (Hint: first calculate the relative formula mass of potassium sulfate, (K_2SO_4)

Answer 1

a) The number of moles of sulfuric acid is 0.04 mol.

b) The number of moles of KOH that reacted is 0.08 mol.

c) The concentration of KOH is 3.2 mol/dm^3.

d) The number of moles of potassium sulfate produced is 0.04 mol.

e) The mass of potassium sulfate produced is 6.96 grams.

Step-by-step explanation:

a) To calculate the number of moles of sulfuric acid, we use the formula:

Moles = Volume (dm^3) × Concentration (mol/dm^3)

Given that the volume is 20 cm^3 and the concentration is 2 mol/dm^3, we can calculate the number of moles:

Moles = 20 cm^3 × (1 dm^3 / 1000 cm^3) × 2 mol/dm^3 = 0.04 mol

So, the number of moles of sulfuric acid added is 0.04 mol.

b) The balanced chemical equation shows that the mole ratio between sulfuric acid and potassium hydroxide is 1:2. Therefore, for every 1 mole of sulfuric acid, 2 moles of potassium hydroxide are consumed. Since 0.04 mol of sulfuric acid was added, the number of moles of potassium hydroxide that reacted is twice that:

Moles of KOH = 2 × 0.04 mol = 0.08 mol

So, the number of moles of KOH that reacted is 0.08 mol.

c) To calculate the concentration of KOH in mol/dm^3, we use the formula:

Concentration (mol/dm^3) = Moles / Volume (dm^3)

Given that the volume is 25 cm^3 and the number of moles is 0.08 mol, we can calculate the concentration:

Concentration = 0.08 mol / (25 cm^3 × (1 dm^3 / 1000 cm^3)) = 3.2 mol/dm^3

So, the concentration of KOH is 3.2 mol/dm^3.

d) The balanced chemical equation shows that the mole ratio between sulfuric acid and potassium sulfate is 1:1. Therefore, the number of moles of potassium sulfate produced is equal to the number of moles of sulfuric acid added:

Moles of K2SO4 = 0.04 mol

So, the number of moles of potassium sulfate produced is 0.04 mol.

e) To calculate the mass of potassium sulfate produced, we first need to determine the relative formula mass of K2SO4. This can be calculated by adding up the relative atomic masses of its elements:

Relative formula mass of K2SO4 = (2 × Relative atomic mass of K) + Relative atomic mass of S + (4 × Relative atomic mass of O)

= (2 × 39) + 32 + (4 × 16) = 174 g/mol

Given that the number of moles of potassium sulfate produced is 0.04 mol, we can calculate the mass:

Mass = Number of moles × Relative formula mass = 0.04 mol × 174 g/mol = 6.96 g

So, the mass of potassium sulfate produced is 6.96 grams.