NEET Some Basic Concepts Of Chemistry — Set 5

Question 1

A 300 mL solution contains 11.7 g of $ \ce{NaCl} $ and has a density of 1.01 g/mL. What is its molarity? (Molar mass: $ \ce{NaCl} $ = 58.5 g/mol)

Accepted Answer

Moles of $ \ce{NaCl} $ = $ \frac{11.7}{58.5} $ = 0.2 mol. Volume = 300 mL = 0.3 L. Molarity = $ \frac{0.2}{0.3} $ ≈ 0.667 M.

Question 2

A gas occupies 0.56 L at STP and weighs 0.64 g. What is its molar mass?

Accepted Answer

Moles = $ \frac{0.56}{22.4} $ = 0.025 mol. Molar mass = $ \frac{0.64}{0.025} $ = 25.6 g/mol.

Question 3

A compound has a molar mass of 180 g/mol and contains 40% carbon, 6.67% hydrogen, and 53.33% oxygen. What is its molecular formula? (Atomic masses: C = 12, H = 1, O = 16)

Accepted Answer

For 100 g: C = 40 g, H = 6.67 g, O = 53.33 g. Moles: C = $ \frac{40}{12} $ ≈ 3.33, H = $ \frac{6.67}{1} $ ≈ 6.67, O = $ \frac{53.33}{16} $ ≈ 3.33. Ratio = 1 : 2 : 1; empirical formula = $ \ce{CH2O} $, mass = 30 g/mol. $ n = \frac{180}{30} = 6 $; molecular formula = $ \ce{C6H12O6} $.

NEET Chemistry: Some Basic Concepts Of Chemistry — Practice Set 5

Q1. A 300 mL solution contains 11.7 g of \( \ce{NaCl} \) and has a density of 1.01 g/mL. What is its molarity? (Molar mass: \( \ce{NaCl} \) = 58.5 g/mol)

Q2. A gas occupies 0.56 L at STP and weighs 0.64 g. What is its molar mass?

Q3. A compound has a molar mass of 180 g/mol and contains 40% carbon, 6.67% hydrogen, and 53.33% oxygen. What is its molecular formula? (Atomic masses: C = 12, H = 1, O = 16)

Q4. A 400 mL solution of \( \ce{HCl} \) has a molarity of 0.25 M and a density of 1.01 g/mL. What is the mass percentage of \( \ce{HCl} \)? (Molar mass: \( \ce{HCl} \) = 36.5 g/mol)

Q5. How many grams of \( \ce{AlCl3} \) are required to produce 5.4 g of \( \ce{Al} \) with excess \( \ce{HCl} \)? (Molar masses: \( \ce{AlCl3} \) = 133.5 g/mol, Al = 27 g/mol)

Q6. How many grams of \( \ce{NaOH} \) are required to produce 11.7 g of \( \ce{NaCl} \) with excess \( \ce{HCl} \)? (Molar masses: \( \ce{NaOH} \) = 40 g/mol, \( \ce{NaCl} \) = 58.5 g/mol)

Q7. What is the mole fraction of \( \ce{CH3OH} \) in a solution containing 8 g of \( \ce{CH3OH} \) and 54 g of \( \ce{H2O} \)? (Molar masses: \( \ce{CH3OH} \) = 32 g/mol, \( \ce{H2O} \) = 18 g/mol)

Q8. How many grams of \( \ce{ZnCl2} \) are required to produce 6.5 g of \( \ce{Zn} \) with excess \( \ce{HCl} \)? (Molar masses: \( \ce{ZnCl2} \) = 136 g/mol, Zn = 65 g/mol)

Q9. A 2 L sample of a gas at STP weighs 1.4 g and contains only carbon and hydrogen. If it produces 4.4 g of \( \ce{CO2} \) on burning, what is its molecular formula? (Atomic masses: C = 12, H = 1)

Q10. How many grams of \( \ce{NaCl} \) are produced when 10.6 g of \( \ce{Na2CO3} \) reacts with excess \( \ce{HCl} \)? (Molar masses: \( \ce{Na2CO3} \) = 106 g/mol, \( \ce{NaCl} \) = 58.5 g/mol)