Mole Concept

Q.

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

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

Q.

Name the twenty most common elements?

Q. The weight of a molecule of the compound $C_{60}{H}_{122}$ is

1. $1.09\times {10}^{-21}g$
2. $5.025\times {10}^{23}g$
3. $16.023\times {10}^{23}g$
4. $1.4\times {10}^{-21}g$

Q.

If Avogadro number $N_A,$ is changed from 6.022 $\times {10}^{23}mo{l}^{-1}$ to 6.022 $\times {10}^{20}mo{l}^{-1},$ what would change?

1. The ratio of chemical species to each other in a balanced equation.

2. The ratio of elements to each other in a compound.

3. The volume of a certain mass of a substance.

4. The mass of one mole of carbon.

Q.

If $\frac{e}{m_e}$ = 1.758820 $\times$ ${10}^{11}$ C ${kg}^{-1}$

The mass of an electron is

1. 9.1094 × 10^-21

2. 6.1094 × 10^-21

3. 6.1094 × 10^-31

4. 9.1094 × 10^-31

Q.

${}_6{C}^{12}$ contains ................... protons and ............. neutrons.

Q.

If the temperature of any gas is increased, its volume:

1. Increases

2. Remains same

3. Decreases

4. None of the above

Q. How many moles of ${\text{CaCO}}_3$ are present in 500 g of ${\text{CaCO}}_3$?
Gram atomic masses Ca, C, and O are 40, 12, and 16 respectively.

1. 5
2. 8
3. 10
4. 6

Q. How many moles of ammonia weigh 85 g?

1. 5

Q.

Hydrogen diffuses 6 times faster than gas X. The molecular mass for X will be___.

1. 72

2. 140

3. 144

4. 100

Q. Calculate the number of molecules present in the 64g of oxygen gas.

Q.

1 mole of water molecules has:

Q.

The gas having same number of molecules as $16g$ of oxygen is

1. 16g. of O3

2. 16g. of SO3

3. 48g. of SO3

4. 1gm of hydrogen

Q. How many mol of C atoms are present in $4\times {10}^{-3}$ mol of glucose?

1. 
2. 
3. 
4. 

Q. If $50\text{g}$ of sugar is present in $450\text{g}$ of water, what is the mass percentage of sugar in the solution.

1. $9\%$
2. $10\%$
3. $50\%$
4. $55\%$

Q. How do we find atomic mass with carbon-12 atom?

Q.

Question 1
Calculate the molecular masses of $H_2,O_2,C{l}_2,C{O}_2,C{H}_4,C_2{H}_6,C_2{H}_4,N{H}_3,C{H}_{3}OH$.

Q.

Question 24
Verify by calculating that

(a) 5 moles of $C{O}_2$ and 5 moles of $H_{2}O$ do not have the same mass.

(b) 240 g calcium and 240 g magnesium elements have a mole ratio of 3:5.

Q. The atomic mass of nitrogen is ______.

1. 14 u
2. 16 u
3. 8 u
4. 7 u

Q. A solution contains 30 g of salt mixed in 90 g of water. What is the concentration of the solution in terms of mass by mass percentage?

1. 25%
2. 50%
3. 33.33%
4. 75%

Q. The number of atoms present in 62 g of phosphorous if its gram atomic mass is 31 g is p $\times {10}^{24}$. What is the value of p?

1. 1.204

Q. A sample is known to contain $2\times 6.022\times {10}^{23}$ hydrogen atoms. How many hydrogen atom does it contain ?

1. $N_A\mathrm{mol}$
2. $\frac{1}{2}\mathrm{mol}$
3. 2mol
4. 1mol

Q.

Question 47
Write the formulae for the following and calculate the molecular mass for each one of them

(a) Caustic potash

(b) Baking powder

(c) Lime Stone

(d) Caustic soda

(e) Ethanol

(f) Common salt

Q. The number of atoms in 4.25 g of $N{H}_3$ is approximately

1. $1\times {10}^{23}$
2. $2\times {10}^{23}$
3. $4\times {10}^{23}$
4. $6\times {10}^{23}$

Q.

Question 27
The difference in the mass of 100 moles each of sodium atoms and sodium ions is 5.48002 g.Compute the mass of an electron.

Q. Calculate the number of aluminium ions $\left(A{l}^{3+}\right)$ present in 0.102 g of aluminium oxide $(A{l}_2{O}_3$).
[Molar mass of Al = 27 g/mol; Molar mass of O = 16 g/mol]

Q. The atomic weight of oxygen is 15.994 u. What is the weight of one atom of oxygen in a gram?

Q.

Calculate the molecular mass of Calcium carbonate $\left({\mathrm{CaCO}}_3\right)$

Given Atomic masses: Ca = 40u, C = 12u, O = 16u

Q.

The molar mass of Z is 20 g. Find the mass of 1 atom of Z.

1. 2.65*10^-23gm

2. 3.32*10^-23gm

3. 5.32*10^-23gm

4. 4.32*10^-23gm

Q. Question 9(b)
What is the mass of:
(b)0.5 mole of water molecules?