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

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

Mole fraction of solute in a 1.00 molal aqueous solution is:
1.  0.0177
2.  0.0344
3.  1.770
4.  0.1770

10 g of hydrogen and 64 of oxygen were filled in a steel vessel and exploded. The amount of water produced in this reaction will be:

1. 2 mol

2. 3 mol

3. 4 mol

4. 1 mol

The volume occupied by one water molecule (density = 1 g cm^-3) is:

1. $9.0\times {10}^{-23}$ $$ ${\mathrm{cm}}^3$

2. $6.023\times {10}^{-23}$ $$ ${\mathrm{cm}}^3$

3. $3.0\times {10}^{-23}$ $$ ${\mathrm{cm}}^3$

4. $5.5\times {10}^{-23}$ $$ ${\mathrm{cm}}^3$

The volume of oxygen gas (O₂) needed to completely burn 1 L of propane gas (C₃H₈)  (both O₂ & propane measured at 0°C and 1 atm) will be:
1. 7 L
2. 6 L
3. 5 L
4. 10 L

When \(1.0\text{ g}\) of magnesium (\(\text{Mg}\)) is reacted with \(0.56\text{ g}\) of oxygen (\(\text{O}_2\)) in a closed container, determine the reactant left in excess and calculate the mass of the excess reactant remaining after the reaction is complete: (At. wt. Mg = 24; O = 16)