How NEET Chemistry Works — Practice

Question 1

The number of moles in 36 g of water (H₂O, molar mass 18 g/mol) is:
(a) 2 (b) 1 (c) 36 (d) 0.5

Accepted Answer

(a) 2.

n = mass/molar mass = 36/18 = 2 mol.

Question 2

The number of molecules in 1 mole of any substance is:
(a) 6.022×10²³ (b) 3.011×10²³ (c) 12.044×10²³ (d) 6.022×10²²

Accepted Answer

(a) 6.022×10²³.

This is Avogadro's number, N_A — the number of particles in one mole.

Question 3

The volume occupied by 1 mole of an ideal gas at STP is:
(a) 22.4 L (b) 11.2 L (c) 44.8 L (d) 1 L

Accepted Answer

(a) 22.4 L.

At STP (0 °C, 1 atm) one mole of any ideal gas occupies 22.4 litres.

Question 4

The molarity of a solution containing 0.5 mol of solute in 250 mL of solution is:
(a) 2 M (b) 0.5 M (c) 1 M (d) 0.25 M

Accepted Answer

(a) 2 M.

M = n/V(L) = 0.5/0.250 = 2 M. Convert millilitres to litres before dividing.

Question 5

The molar mass of CO₂ (C = 12, O = 16) is:
(a) 44 g/mol (b) 28 g/mol (c) 12 g/mol (d) 16 g/mol

Accepted Answer

(a) 44 g/mol.

M = 12 + 2×16 = 12 + 32 = 44 g/mol.

Question 6

The number of oxygen atoms in 1 mole of CO₂ is:
(a) 1.2044×10²⁴ (b) 6.022×10²³ (c) 3.011×10²³ (d) 2

Accepted Answer

(a) 1.2044×10²⁴.

One mole of CO₂ has 2 moles of O atoms = 2 × 6.022×10²³ = 1.2044×10²⁴ atoms.

Question 7

The percentage by mass of nitrogen in NH₃ (N = 14, H = 1) is approximately:
(a) 82% (b) 18% (c) 50% (d) 14%

Accepted Answer

(a) 82%.

Molar mass = 14 + 3 = 17; %N = (14/17)×100 ≈ 82.4%.

Question 8

In the reaction N₂ + 3H₂ → 2NH₃, if 1 mole of N₂ reacts with 2 moles of H₂, the limiting reagent is:
(a) H₂ (b) N₂ (c) NH₃ (d) neither

Accepted Answer

(a) H₂.

1 mole N₂ needs 3 moles H₂; only 2 are available, so H₂ runs out first and limits the yield. N₂ is in excess.

Practice — How NEET Chemistry Works