Some Basic Concepts of Chemistry · Question 33

The number of atoms in 0.1 mol of a triatomic gas is ( NA = 6.02 1023 mol-1)

1. 6.026 1022
2. 1.806 1023
3. 3.600 1023
4. 1.800 1022

25.3 g of sodium carbonate, Na2CO3 is dissolved in enough water to make 250 mL of solution. If sodium carbonate dissociates completely, molar concentration of sodium ion, Na+ and carbonate ions, CO32- are respectively (Molar mass of Na2CO3 = 106 g mol-1)

1. 0.955 M and 1.910 M
2. 1.910 M and 0.955 M
3. 1.90 M and 1.910 M
4. 0.477 M and 0.477 M

10 g of hydrogen and 64 g of oxygen were filled in a steel vessel and exploded. Amount of water produced in this reaction will be

1. 3 mol
2. 4 mol
3. 1 mol
4. 2 mol

What volume of oxygen gas (O2) measured at 0 C and 1 atm, is needed to burn completely 1 L of propane gas (C3H8) measured under the same conditions?

1. 5 L
2. 10 L
3. 7 L
4. 6 L

How many moles of lead (II) chloride will be formed from a reaction between 6.5 g of PbO and 3.2 g of HCl?

1. 0.011
2. 0.029
3. 0.044
4. 0.333

An organic compound contains carbon, hydrogen and oxygen. Its elemental analysis gave C, 38.71% and H, 9.67%. The empirical formula of the compound would be

1. CHO
2. CH4O
3. CH3O
4. CH2O

Volume occupied by one molecule of water (density = 1 g cm-3) is

1. 3.0 10-23 cm3
2. 5.5 10-23 cm3
3. 9.0 10-23 cm3
4. 6.023 10-23 cm3

An element, X has the following isotopic composition: 200X : 90\% 199X : 8.0\% 202X : 2.0\% The weighted average atomic mass of the naturally occurring element X is closest to

1. 201 amu
2. 202 amu
3. 199 amu
4. 200 amu

Concentrated aqueous sulphuric acid is 98% H2SO4 by mass and has a density of 1.80 g mL-1. Volume of acid required to make one litre of 0.1 M H2SO4 solution is

1. 16.65 mL
2. 22.20 mL
3. 5.55 mL
4. 11.10 mL

The maximum number of molecules is present in

1. 15 L of H2 gas at STP
2. 5 L of N2 gas at STP
3. 0.5 g of H2 gas
4. 10 g of O2 gas