The highest number of atoms is present in -

1. 52 moles of Ar

2. 52 u of He

3. 52 g of He.

4. All of the above have the same number of atoms

Burning a small sample of welding gas (constituted of C and H only)  in oxygen gives 3.38 g carbon dioxide, 0.690 g of water, and no other products. A volume of 10.0 L (measured at STP) of this welding gas is found to weigh 11.6 g. Molecular formula of welding gas would be -

1. C₂H₂

2. C₂H₆

3. CH

4. C₂H₄

The mass of CaCO₃ required to react completely with 25 mL of 0.75 M HCl according to the given reaction would be:

CaCO_3(s) + HCl_(aq) ➡ CaCl_2(aq) + CO_2(g) + H₂O_(l) 

1. 0.36 g

2. 0.09 g

3. 0.96 g

4. 0.66 g

Amount of HCl that would react with 5.0 g of manganese dioxide, as per the
given reaction will be:
4HCl_(aq) + MnO_2(s) ➡ 2H₂O_(l) + MnCl_2(aq) + Cl₂₍₂₎

1. 4.8 g

2. 6.4 g

3. 2.8 g

4. 8.4 g

The numbers 234,000 and 6.0012 can be represented in scientific notation as -

1. $2.34\times {10}^{-9} \mathrm{and} 6\times {10}^3$

2. 0.234 $\times {10}^{-6}$ and $60012\times {10}^{-9}$

3. $2.34\times {10}^{-9} \mathrm{and}$ $6.0012\times {10}^{-9}$

4. 2.34$\times {10}^5$ and 6.0012$\times {10}^0$

The number of significant figures in the numbers 5005, 500.0, and 126,000 are, respectively: 

0.50 mol  Na₂CO₃ and 0.50 M Na₂CO₃ are different because:

Round up the following number into three significant figures: 
i. 10.4107  ii. 0.04597 respectively  are 

The following data was obtained when dinitrogen and dioxygen react together to form different compounds:

The law of chemical combination applicable to the above experimental data is:
1. Law of reciprocal proportions
2. Law of multiple proportions
3. Law of constant composition
4. None of these.