NEET Some Basic Concepts Of Chemistry — Set 12

Question 1

A mixture of 5 g $ \ce{H2} $ and 40 g $ \ce{O2} $ is ignited to form $ \ce{H2O} $. What is the mass of $ \ce{H2O} $ produced? (Atomic masses: H = 1, O = 16)

Accepted Answer

Reaction: $ \ce{2H2 + O2 -> 2H2O} $. Moles: $ \ce{H2} $ = $ \frac{5}{2} $ = 2.5 mol, $ \ce{O2} $ = $ \frac{40}{32} $ = 1.25 mol. 2 mol $ \ce{H2} $ need 1 mol $ \ce{O2} $; 1.25 mol $ \ce{O2} $ limits, reacts with 2.5 mol $ \ce{H2} $ (available). 2.5 mol $ \ce{H2O} $ formed = 2.5 × 18 = 45 g.

Question 2

A compound contains 40% carbon, 6.67% hydrogen, and 53.33% oxygen by mass. What is its empirical 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} $.

Question 3

How many moles of $ \ce{CH4} $ are required to produce 88 g of $ \ce{CO2} $ if the reaction yield is 50%? (Molar mass: $ \ce{CH4} $ = 16 g/mol, $ \ce{CO2} $ = 44 g/mol)

Accepted Answer

Reaction: $ \ce{CH4 + 2O2 -> CO2 + 2H2O} $. Moles of $ \ce{CO2} $ = $ \frac{88}{44} $ = 2 mol. With 50% yield, actual $ \ce{CH4} $ moles = $ \frac{2}{0.5} $ = 4 mol.

NEET Chemistry: Some Basic Concepts Of Chemistry — Practice Set 12

Q1. A mixture of 5 g \( \ce{H2} \) and 40 g \( \ce{O2} \) is ignited to form \( \ce{H2O} \). What is the mass of \( \ce{H2O} \) produced? (Atomic masses: H = 1, O = 16)

Q2. A compound contains 40% carbon, 6.67% hydrogen, and 53.33% oxygen by mass. What is its empirical formula? (Atomic masses: C = 12, H = 1, O = 16)

Q3. How many moles of \( \ce{CH4} \) are required to produce 88 g of \( \ce{CO2} \) if the reaction yield is 50%? (Molar mass: \( \ce{CH4} \) = 16 g/mol, \( \ce{CO2} \) = 44 g/mol)

Q4. What is the mass of \( \ce{BaSO4} \) produced when 20 g of \( \ce{BaCl2} \) reacts with excess \( \ce{H2SO4} \)? (Molar masses: \( \ce{BaCl2} \) = 208 g/mol, \( \ce{BaSO4} \) = 233 g/mol)

Q5. A solution contains 20 ppm of \( \ce{MgCl2} \) by mass in water. What is its molality? (Molar mass: \( \ce{MgCl2} \) = 95 g/mol)

Q6. How many grams of \( \ce{FeSO4} \) are required to produce 11.2 g of \( \ce{Fe} \) with excess \( \ce{H2} \)? (Molar masses: \( \ce{FeSO4} \) = 152 g/mol, Fe = 56 g/mol)

Q7. How many grams of \( \ce{CuO} \) are required to produce 8 g of \( \ce{Cu} \) with excess \( \ce{CO} \)? (Molar masses: \( \ce{CuO} \) = 79.5 g/mol, Cu = 64 g/mol)

Q8. A compound contains 26.67% carbon, 2.22% hydrogen, and 71.11% oxygen by mass. If its molar mass is 90 g/mol, what is its molecular formula? (Atomic masses: C = 12, H = 1, O = 16)

Q9. A 250 mL solution contains 4.8 g of \( \ce{NaCl} \) and has a density of 1.02 g/mL. What is the molarity? (Molar mass: \( \ce{NaCl} \) = 58.5 g/mol)

Q10. A gas occupies 11.2 L at STP and weighs 16 g. What is its molar mass?