Some Basic Concepts of Chemistry

Molality (m) of 3M aqueous solution of NaCl is : (Given : Density of solution = 1.25 g mL-1, Molar mass in g mol-1 : Na - 23, Cl - 35.5)

1. 2.90 m
2. 3.85 m
3. 1.90 m
4. 2.79 m

The incorrect postulates of the Dalton's atomic theory are : Choose the correct answer from the options given below :

1. (B), (D) only
2. (A), (B), (D) only
3. (B), (D), (E) only
4. (C), (D), (E) only

An organic compound has 42.1\% carbon, 6.4\% hydrogen and the remainder is oxygen. If its molecular weight is 342, then its molecular formula is :

1. C14H20O10
2. C12H22O11
3. C12H20O12
4. C11H18O12

The number of moles of methane required to produce 11 g CO2(g) after complete combustion is : (Given molar mass of methane in g mol-1 : 16)

1. 0.35
2. 0.25
3. 0.5
4. 0.75

The Molarity (M) of an aqueous solution containing 5.85 g of NaCl in 500 mL water is : (Given : Molar Mass Na : 23 and Cl : 35.5 g mol-1)

1. 20
2. 4
3. 2
4. 0.2

Choose the Incorrect Statement about Dalton's Atomic Theory

1. Compounds are formed when atoms of different elements combine in any ratio.
2. Matter consists of indivisible atoms.
3. Chemical reactions involve reorganization of atoms
4. All the atoms of a given element have identical properties including identical mass.

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