NEET Some Basic Concepts Of Chemistry — Set 2

Question 1

What is the mass percentage of $ \ce{KNO3} $ in a solution made by dissolving 10.1 g of $ \ce{KNO3} $ in 40 g of water? (Molar mass: $ \ce{KNO3} $ = 101 g/mol)

Accepted Answer

Total mass = 10.1 + 40 = 50.1 g. Mass % = $ \frac{10.1}{50.1} $ × 100 ≈ 20.16%.

Question 2

A compound contains 27.27% carbon and 72.73% oxygen by mass. What is its empirical formula? (Atomic masses: C = 12, O = 16)

Accepted Answer

For 100 g: C = 27.27 g, O = 72.73 g. Moles: C = $ \frac{27.27}{12} $ ≈ 2.27, O = $ \frac{72.73}{16} $ ≈ 4.55. Ratio = 1 : 2; empirical formula = $ \ce{CO2} $.

Question 3

How many grams of $ \ce{Al2O3} $ are required to produce 10.8 g of $ \ce{Al} $ with excess $ \ce{CO} $? (Molar masses: $ \ce{Al2O3} $ = 102 g/mol, Al = 27 g/mol)

Accepted Answer

Reaction: $ \ce{Al2O3 + 3CO -> 2Al + 3CO2} $. Moles of Al = $ \frac{10.8}{27} $ = 0.4 mol. 2 mol Al from 1 mol $ \ce{Al2O3} $; 0.4 mol from 0.2 mol. Mass = 0.2 × 102 = 20.4 g.

NEET Chemistry: Some Basic Concepts Of Chemistry — Practice Set 2

Q1. What is the mass percentage of \( \ce{KNO3} \) in a solution made by dissolving 10.1 g of \( \ce{KNO3} \) in 40 g of water? (Molar mass: \( \ce{KNO3} \) = 101 g/mol)

Q2. A compound contains 27.27% carbon and 72.73% oxygen by mass. What is its empirical formula? (Atomic masses: C = 12, O = 16)

Q3. How many grams of \( \ce{Al2O3} \) are required to produce 10.8 g of \( \ce{Al} \) with excess \( \ce{CO} \)? (Molar masses: \( \ce{Al2O3} \) = 102 g/mol, Al = 27 g/mol)

Q4. What volume of \( \ce{CO2} \) at STP is produced when 9 g of \( \ce{C3H8} \) is burned completely? (Molar mass: \( \ce{C3H8} \) = 44 g/mol)

Q5. A solution contains 30 ppm of \( \ce{Na2SO4} \) by mass in water. What is its molarity if the density is 1 g/mL? (Molar mass: \( \ce{Na2SO4} \) = 142 g/mol)

Q6. What volume of \( \ce{O2} \) at STP is required to burn 5.6 g of \( \ce{C2H4} \) completely to \( \ce{CO2} \) and \( \ce{H2O} \)? (Molar mass: \( \ce{C2H4} \) = 28 g/mol)

Q7. A 2.5 L sample of a gas at STP has a mass of 5 g. If it contains only nitrogen and oxygen, what is its empirical formula? (Atomic masses: N = 14, O = 16)

Q8. How many grams of \( \ce{K2SO4} \) are produced when 11.2 g of \( \ce{KOH} \) reacts with excess \( \ce{H2SO4} \)? (Molar masses: \( \ce{KOH} \) = 56 g/mol, \( \ce{K2SO4} \) = 174 g/mol)

Q9. What is the mass of \( \ce{FeCl2} \) produced when 11.2 g of \( \ce{Fe} \) reacts with excess \( \ce{HCl} \)? (Molar masses: Fe = 56 g/mol, \( \ce{FeCl2} \) = 126.5 g/mol)

Q10. What is the mass of \( \ce{CaCl2} \) produced when 25 g of \( \ce{Ca(OH)2} \) reacts with excess \( \ce{HCl} \)? (Molar masses: \( \ce{Ca(OH)2} \) = 74 g/mol, \( \ce{CaCl2} \) = 111 g/mol)