Some Basic Concepts of Chemistry

Consider the following reaction : 3PbCl2 + 2(NH4)3PO4 Pb3(PO4)2 + 6NH4Cl If 72 mmol of PbCl2 is mixed with 50 mmol of (NH4)3PO4, then the amount of Pb3(PO4)2 formed is mmol (nearest integer).

10 mL of gaseous hydrocarbon on combustion gives 40 mL of CO2(g) and 50 mL of water vapour. Total number of carbon and hydrogen atoms in the hydrocarbon is .

Number of moles of methane required to produce 22 g CO2(g) after combustion is x 10-2 moles. The value of x is .

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. 1.187 g CaCO3 + 1.187 g MgCO3
2. 1.187 g CaCO3 + 1.023 g MgCO3
3. 1.023 g CaCO3 + 1.187 g MgCO3
4. 1.023 g CaCO3 + 1.023 g MgCO3

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)

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)

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)

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]

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.

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)