On complete combustion, 44 g of a sample of a compound gives 88 g CO₂ and 36 g of H₂O. The molecular formula of the compound may be:

1.  ${\mathrm{C}}_4{\mathrm{H}}_6$ $$

2.  ${\mathrm{C}}_2{\mathrm{H}}_6\mathrm{O}$ $$

3.  ${\mathrm{C}}_2{\mathrm{H}}_4\mathrm{O}$

4.  ${\mathrm{C}}_3{\mathrm{H}}_6\mathrm{O}$

 The maximum number of molecules is present in which of the following? 

1. 15 L of $H_2$ gas at STP

2. 5 L of $N_2$ gas at STP

3. 0.5 g of $H_2$ gas

4. 10 g of $O_2$ gas

The number of  moles  present in 2.5 litres of 0.2 M  ${\mathrm{H}}_2{\mathrm{SO}}_4$ are:

1. 0.25

2. 0.5

3. 0.75

4. 0.2

Which of the following statements is correct?

1. 1 mole of electrons weights 5.4 mg .
2. 1 mole of electrons weights 5.4 kg. 
3. 1 mole of electrons weights 0.54 mg. 
4. 1 mole of electrons has 1.6$\times {10}^{-19}$ C of charge.

1cc N₂O at STP contains: 

The number of valence electrons present in 0.53 grams of Na₂CO₃ is:

1. $3.01\times {10}^{23}$

2. $7.22\times {10}^{22}$

3. $12.046\times {10}^{23}$

4. $6.023\times {10}^{23}$

At STP, the density of CCl₄ vapour in g/L will be closest to: 

1. 8.67

2. 6.87

3. 3.67

4. 4.26

The weight of 1x10²³ molecules of CuSO₄.5H₂O is: 

1. 42.42 g

2. 41.42 g

3. 44.44 g

4. 48.94 g

lf N_A is Avogadro's number, then the number of valence electrons in 4.2 g of nitride ions (N${}^{3-}$) will be:

Determine the number of significant figures in the final answer of the expression \(\large{\frac{(29.2-20.2)\times(1.79\times10^5)}{1.37}}\):