Some Basic Concepts of Chemistry

The number of hydrogen atoms present in 5.4 g of urea is : (Given : Molar mass of urea : 60 g mol-1, NA : 6.022 × 1023 particles mol-1)

1. 2.168 × 1022
2. 2.168 × 1023
3. 1.084 × 1022
4. 1.084 × 1023

Among the following, choose the ones with equal number of atoms. Choose the correct answer from the options given below:

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

The highest number of helium atoms is in

1. 4 mol of helium
2. 4u of helium
3. 4 g of helium
4. 2.271098 L of helium at STP

1.0 g of H2 has same number of molecules as in:

1. 14 g of N2
2. 18 g of H2O
3. 16 g of CO
4. 28 g of N2

Which one of the following has maximum number of atoms?

1. 1 g of Mg(s) [Atomic mass of Mg = 24]
2. 1 g of O2(g) [Atomic mass of O = 16]
3. 1 g of Li(s) [Atomic mass of Li = 7]
4. 1 g of Ag(s) [Atomic mass of Ag = 108]

In which case is number of molecules of water maximum?

1. 18 mL of water
2. 0.18 g of water
3. 0.00224 L of water vapours at 1 atm and 273 K
4. 10-3 mol of water

Suppose the elements X and Y combine to form two compounds XY2 and X3Y2. When 0.1 mole of XY2 weighs 10 g and 0.05 mole of X3Y2 weighs 9 g, the atomic weights of X and Y are

1. 40, 30
2. 60, 40
3. 20, 30
4. 30, 20

If Avogadro number NA, is changed from 6.022 1023 mol-1 to 6.022 1020 mol-1, this would change

1. the mass of one mole of carbon
2. the ratio of chemical species to each other in a balanced equation
3. the ratio of elements to each other in a compound
4. the definition of mass in units of grams.

The number of water molecules is maximum in

1. 1.8 gram of water
2. 18 gram of water
3. 18 moles of water
4. 18 molecules of water

A mixture of gases contains H2 and O2 gases in the ratio of 1 : 4 (w/w). What is the molar ratio of the two gases in the mixture ?

1. 16 : 1
2. 2 : 1
3. 1 : 4
4. 4 : 1

Which has the maximum number of molecules among the following ?

1. 44 g CO2
2. 48 g O3
3. 8 g H2
4. 64 g SO2

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

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

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

Which has maximum molecules?

1. 7 g N2
2. 2 g H2
3. 16 g NO2
4. 16 g O2

Specific volume of cylindrical virus particle is 6.02 10-2 cc/g whose radius and length are 7 A and 10 A respectively. If NA = 6.02 1023, find molecular weight of virus.

1. 15.4 kg/mol
2. 1.54 104 kg/mol
3. 3.08 104 kg/mol
4. 3.08 103 kg/mol