Some Basic Concepts of Chemistry

JEE Main 2024 (Online) 31st January Evening ShiftMCQMedium📈 Topic in 42% papers+4−1

Ques. 1JEE Main 2024, 31 January (Evening Shift)

A sample of CaCO3 and MgCO3 weighed 2.21 g is ignited to constant weight of 1.152 g. The composition of mixture is : (Given molar mass in g mol-1 CaCO3 : 100, MgCO3 : 84)

1.187 g CaCO3 + 1.187 g MgCO3
1.187 g CaCO3 + 1.023 g MgCO3
1.023 g CaCO3 + 1.187 g MgCO3
1.023 g CaCO3 + 1.023 g MgCO3

Answer

(2) 1.187 g CaCO3 + 1.023 g MgCO3

Solution

CaCO3 CaO + CO2 ; MgCO3 MgO + CO2

Let mass of CaCO3 = x g ⇒ mass of MgCO3 = (2.21 − x) g

∵ 1 mol carbonate gives 1 mol oxide (CaO = 56, MgO = 40):

56x100 + 40(2.21 - x)84 = 1.152

0.560x + 1.0524 - 0.4762x = 1.152

0.0838x = 0.0996 x 1.187 g

∴ CaCO3 = 1.187 g

MgCO3 = 2.21 − 1.187 = 1.023 g

Answer: (2)

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Ques. 2JEE Main 2024, 31 January (Evening Shift)

The molarity of 1 L orthophosphoric acid (H3PO4) having 70% purity by weight (specific gravity 1.54 g cm-3) is M. (Molar mass of H3PO4 = 98 g mol-1)

Ques. 3JEE Main 2024, 30 January (Morning Shift)

The mass of sodium acetate (CH3COONa) required to prepare 250 mL of 0.35 M aqueous solution is g. (Molar mass of CH3COONa is 82.02 g mol-1)

Ques. 4JEE Main 2024, 30 January (Morning Shift)

0.05 cm thick coating of silver is deposited on a plate of 0.05 m2 area. The number of silver atoms deposited on plate are 1023. (At mass Ag = 108, d = 7.9 g cm-3)

Ques. 5JEE Main 2024, 29 January (Morning Shift)

A solution of H2SO4 is 31.4% H2SO4 by mass and has a density of 1.25 g/mL. The molarity of the H2SO4 solution is M (nearest integer) [Given molar mass of H2SO4 = 98 g mol-1]

Ques. 6JEE Main 2024, 29 January (Evening Shift)

If 50 mL of 0.5 M oxalic acid is required to neutralise 25 mL of NaOH solution, the amount of NaOH in 50 mL of given NaOH solution is g.

Ques. 7JEE Main 2024, 27 January (Morning Shift)

Mass of methane required to produce 22 g of CO2 after complete combustion is g. (Given Molar mass in g mol-1 C = 12.0, H = 1.0, O = 16.0)

Ques. 8JEE Main 2024, 27 January (Evening Shift)

Volume of 3M NaOH (formula weight 40 g mol-1) which can be prepared from 84 g of NaOH is 10-1dm3.

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