Some Basic Concepts of Chemistry

When 1 dm3 of CO2 gas is passed over hot coke, the volume of gaseous mixture after complete reaction at STP becomes 1.4 dm3. The composition of the gaseous mixture at STP is :

1. 0.6 dm3 of CO, 0.8 dm3 of CO2
2. 0.8 dm3 of CO, 0.8 dm3 of CO2
3. 0.6 dm3 of CO, 0.4 dm3 of CO2
4. 0.8 dm3 of CO, 0.6 dm3 of CO2

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

The numbers 17.0145 and 21.0235 were rounded to three figures after the decimal point. The resulting numbers, respectively, are

1. 17.015 and 21.024
2. 17.014 and 21.023
3. 17.015 and 21.023
4. 17.014 and 21.024

The amount of carbon dioxide evolved upon complete combustion of 116 g of n-butane is (Given: atomic mass in amu H = 1, C = 12 and O = 16)

1. 362 g
2. 352 g
3. 322 g
4. 176 g

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

Dalton's Atomic theory could not explain which of the following?

1. Law of multiple proportion
2. Law of gaseous volume
3. Law of conservation of mass
4. Law of constant proportion

1 gram of sodium hydroxide was treated with 25 mL of 0.75 M HCl solution, the mass of sodium hydroxide left unreacted is equal to

1. 750 mg
2. 250 mg
3. Zero mg
4. 200 mg

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

A compound X contains 32\% of A, 20\% of B and remaining percentage of C. Then, the empirical formula of X is : (Given atomic masses of A=64 ; B=40 ; C=32 u)

1. A2BC2
2. ABC3
3. AB2C2
4. ABC4

The amount of glucose required to prepare 250 mL of M20 aqueous solution is : (Molar mass of glucose : 180 g mol-1)

1. 2.25 g
2. 4.5 g
3. 0.44 g
4. 1.125 g

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

The right option for the mass of CO2 produced by heating 20 g of 20\% pure limestone is (Atomic mass of Ca = 40) [ CaCO3 1200 K CaO + CO2]

1. 1.76 g
2. 2.64 g
3. 1.32 g
4. 1.12 g

In one molal solution that contains 0.5 mole of a solute, there is

1. 500 mL of solvent
2. 500 g of solvent
3. 100 mL of solvent
4. 1000 g of solvent

What mass of 95% pure CaCO3 will be required to neutralise 50 mL of 0.5 M HCl solution according to the following reaction? CaCO3(s) + 2HCl(aq) CaCl2(aq) + CO2(g) + 2H2O(l) [Calculate upto second place of decimal point]

1. 1.25 g
2. 1.32 g
3. 3.65 g
4. 9.50 g

The density of the solution is 2.15 g mL-1, then mass of 2.5 mL solution in correct significant figures is :

1. 53.75 g
2. 5375 10-3 g
3. 5.4 g
4. 5.38 g

An organic compound contains 78% (by wt.) carbon and remaining percentage of hydrogen. The right option for the empirical formula of this compound is : [Atomic wt. of C is 12, H is 1]

1. CH4
2. CH
3. CH2
4. CH3

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]

The number of moles of hydrogen molecules required to produce 20 moles of ammonia through Haber’s process is :

1. 10
2. 20
3. 30
4. 40

A mixture of 2.3 g formic acid and 4.5 g oxalic acid is treated with conc. H2SO4. The evolved gaseous mixture is passed through KOH pellets. Weight (in g) of the remaining product at STP will be

1. 1.4
2. 3.0
3. 2.8
4. 4.4

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

What is the mass of the precipitate formed when 50 mL of 16.9\% solution of AgNO3 is mixed with 50 mL of 5.8\% NaCl solution ? (Ag = 107.8, N = 14, O = 16, Na = 23, Cl = 35.5)

1. 3.5 g
2. 7 g
3. 14 g
4. 28 g

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

20.0 g of a magnesium carbonate sample decomposes on heating to give carbon dioxide and 8.0 g magnesium oxide. What will be the percentage purity of magnesium carbonate in the sample? (At. wt. of Mg = 24)

1. 96
2. 60
3. 84
4. 75

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

Equal masses of H2, O2 and methane have been taken in a container of volume V at temperature 27 in identical conditions. The ratio of the volumes of gases H2 : O2 : methane would be

1. 8 : 16 : 1
2. 16 : 8 : 1
3. 16 : 1 : 2
4. 8 : 1 : 2

When 22.4 litres of H2(g) is mixed with 11.2 litres of Cl2(g), each at S.T.P. the moles of HCl(g) formed is equal to

1. 1 mol of HCl(g)
2. 2 mol of HCl(g)
3. 0.5 mol of HCl(g)
4. 1.5 mol of HCl(g)

1.0 g of magnesium is burnt with 0.56 g O2 in a closed vessel. Which reactant is left in excess and how much ? (At. wt. Mg = 24, O = 16)

1. Mg, 0.16 g
2. O2, 0.16 g
3. Mg, 0.44 g
4. O2, 0.28 g

6.02 1020 molecules of urea are present in 100 mL of its solution. The concentration of solution is

1. 0.001 M
2. 0.1 M
3. 0.02 M
4. 0.01 M