NEET Some Basic Concepts Of Chemistry — Set 19

Question 1

How many grams of $ \ce{MgCl2} $ are produced when 9.5 g of $ \ce{Mg(OH)2} $ reacts with excess $ \ce{HCl} $? (Molar masses: $ \ce{Mg(OH)2} $ = 58 g/mol, $ \ce{MgCl2} $ = 95 g/mol)

Accepted Answer

Reaction: $ \ce{Mg(OH)2 + 2HCl -> MgCl2 + 2H2O} $. Moles of $ \ce{Mg(OH)2} $ = $ \frac{9.5}{58} $ ≈ 0.1638 mol. 1 mol $ \ce{Mg(OH)2} $ produces 1 mol $ \ce{MgCl2} $; mass = 0.1638 × 95 ≈ 15.56 g.

Question 2

A 0.15 M $ \ce{KOH} $ solution is diluted by adding 150 mL of water to 50 mL of the original solution. What is the final molarity?

Accepted Answer

$ M_1 V_1 = M_2 V_2 $. 0.15 × 50 = $ M_2 $ × (50 + 150). $ M_2 = \frac{0.15 \times 50}{200} = 0.0375 $ M.

Question 3

What is the mole fraction of $ \ce{NaCl} $ in a solution made by dissolving 5.85 g of $ \ce{NaCl} $ in 90 g of water? (Molar masses: $ \ce{NaCl} $ = 58.5 g/mol, $ \ce{H2O} $ = 18 g/mol)

Accepted Answer

Moles of $ \ce{NaCl} $ = $ \frac{5.85}{58.5} $ = 0.1 mol. Moles of $ \ce{H2O} $ = $ \frac{90}{18} $ = 5 mol. Total moles = 0.1 + 5 = 5.1; mole fraction = $ \frac{0.1}{5.1} $ ≈ 0.0196.

NEET Chemistry: Some Basic Concepts Of Chemistry — Practice Set 19

Q1. How many grams of \( \ce{MgCl2} \) are produced when 9.5 g of \( \ce{Mg(OH)2} \) reacts with excess \( \ce{HCl} \)? (Molar masses: \( \ce{Mg(OH)2} \) = 58 g/mol, \( \ce{MgCl2} \) = 95 g/mol)

Q2. A 0.15 M \( \ce{KOH} \) solution is diluted by adding 150 mL of water to 50 mL of the original solution. What is the final molarity?

Q3. What is the mole fraction of \( \ce{NaCl} \) in a solution made by dissolving 5.85 g of \( \ce{NaCl} \) in 90 g of water? (Molar masses: \( \ce{NaCl} \) = 58.5 g/mol, \( \ce{H2O} \) = 18 g/mol)

Q4. How many significant figures are present in the result of \( \frac{0.0256 \times 273.15}{0.0821} \)?

Q5. A solution of \( \ce{H2SO4} \) has a molarity of 0.5 M and a density of 1.03 g/mL. What is its molality? (Molar mass: \( \ce{H2SO4} \) = 98 g/mol)

Q6. What is the mass percentage of \( \ce{KOH} \) in a solution made by dissolving 5.6 g of \( \ce{KOH} \) in 44.4 g of water? (Molar mass: \( \ce{KOH} \) = 56 g/mol)

Q7. How many grams of \( \ce{CuSO4} \) are required to produce 12.8 g of \( \ce{Cu} \) with excess \( \ce{Zn} \)? (Molar masses: \( \ce{CuSO4} \) = 159.5 g/mol, Cu = 64 g/mol)

Q8. What volume of \( \ce{O2} \) at STP is required to burn 7.8 g of \( \ce{C3H6} \) completely to \( \ce{CO2} \) and \( \ce{H2O} \)? (Molar mass: \( \ce{C3H6} \) = 42 g/mol)

Q9. A 10 L sample of a gas at STP weighs 11.6 g and contains only C and H. If it produces 3.38 g \( \ce{CO2} \) on burning, what is its molecular formula? (Atomic masses: C = 12, H = 1)

Q10. A 250 mL solution contains 9.75 g of \( \ce{HNO3} \) and has a density of 1.03 g/mL. What is its molarity? (Molar mass: \( \ce{HNO3} \) = 63 g/mol)