NEET Some Basic Concepts Of Chemistry — Set 6

Question 1

How many significant figures are present in the result of $ \frac{0.0567 \times 298.15}{0.101} $?

Accepted Answer

0.0567 (3 sig figs), 298.15 (5 sig figs), 0.101 (3 sig figs). Result ≈ 167.34; limited to 3 sig figs (167).

Question 2

A compound contains 38.71% carbon, 9.68% hydrogen, and 51.61% oxygen by mass. What is its empirical formula? (Atomic masses: C = 12, H = 1, O = 16)

Accepted Answer

For 100 g: C = 38.71 g, H = 9.68 g, O = 51.61 g. Moles: C = $ \frac{38.71}{12} $ ≈ 3.23, H = $ \frac{9.68}{1} $ ≈ 9.68, O = $ \frac{51.61}{16} $ ≈ 3.23. Ratio = 1 : 3 : 1; empirical formula = $ \ce{CH3O} $.

Question 3

What is the mass of $ \ce{BaCl2} $ produced when 26.1 g of $ \ce{Ba(OH)2} $ reacts with excess $ \ce{HCl} $? (Molar masses: $ \ce{Ba(OH)2} $ = 171 g/mol, $ \ce{BaCl2} $ = 208 g/mol)

Accepted Answer

Reaction: $ \ce{Ba(OH)2 + 2HCl -> BaCl2 + 2H2O} $. Moles of $ \ce{Ba(OH)2} $ = $ \frac{26.1}{171} $ ≈ 0.1526 mol. 1 mol $ \ce{Ba(OH)2} $ produces 1 mol $ \ce{BaCl2} $; mass = 0.1526 × 208 ≈ 31.74 g.

NEET Chemistry: Some Basic Concepts Of Chemistry — Practice Set 6

Q1. How many significant figures are present in the result of \( \frac{0.0567 \times 298.15}{0.101} \)?

Q2. A compound contains 38.71% carbon, 9.68% hydrogen, and 51.61% oxygen by mass. What is its empirical formula? (Atomic masses: C = 12, H = 1, O = 16)

Q3. What is the mass of \( \ce{BaCl2} \) produced when 26.1 g of \( \ce{Ba(OH)2} \) reacts with excess \( \ce{HCl} \)? (Molar masses: \( \ce{Ba(OH)2} \) = 171 g/mol, \( \ce{BaCl2} \) = 208 g/mol)

Q4. A 0.2 M \( \ce{NaCl} \) solution is diluted by adding 250 mL of water to 150 mL of the original solution. What is the final molarity?

Q5. A 0.4 M \( \ce{HCl} \) solution is diluted by adding 200 mL of water to 100 mL of the original solution. What is the final molarity?

Q6. A mixture of 2.3 g ethanol (\( \ce{C2H5OH} \)) and 4.8 g methanol (\( \ce{CH3OH} \)) is dissolved in water to make 250 mL of solution. What is the total molarity of alcohols? (Molar masses: ethanol = 46 g/mol, methanol = 32 g/mol)

Q7. How many significant figures are present in the result of \( \frac{0.0732 \times 310.15}{0.0821} \)?

Q8. A mixture of 6 g \( \ce{H2} \) and 32 g \( \ce{O2} \) is ignited to form \( \ce{H2O} \). What is the mass of \( \ce{H2O} \) produced? (Atomic masses: H = 1, O = 16)

Q9. A compound contains 52.17% carbon, 13.04% hydrogen, and 34.78% oxygen by mass. What is its empirical formula? (Atomic masses: C = 12, H = 1, O = 16)

Q10. What is the mass of \( \ce{MgO} \) produced when 12 g of \( \ce{Mg} \) reacts with 16 g of \( \ce{O2} \)? (Atomic masses: Mg = 24, O = 16)