Question

Which of the following would weigh most?

• A. 1 mole ${\mathrm{H}}_2\mathrm{O}$
• B. 1 mole ${\mathrm{CO}}_2$
• C. 1 mole ${\mathrm{NH}}_3$
• D. 1 mole of $\mathrm{CO}$

Answer 1

The correct option is B

1 mole ${\mathrm{CO}}_2$

Explanation of the correct option :

(B) 1 mol of ${\mathrm{CO}}_2$ = Molecular mass of ${\mathrm{CO}}_2$

Molecular mass of water = (Mass of carbon +2×Mass of oxygen)

= {12+(2x16)}

= 44g

Explanation of the incorrect option :

(A) 1 mol of ${\mathrm{H}}_2\mathrm{O}$ = Molecular mass of ${\mathrm{H}}_2\mathrm{O}$

Molecular mass of water = (2×Mass of hydrogen+Mass of oxygen)

= (2×1+16)

= 18g

(C) 1 mol of ${\mathrm{NH}}_3$ = Molecular mass of ${\mathrm{NH}}_3$

Molecular mass of water = (Mass of nitrogen +3×Mass of hydrogen)

= {14+(3x1)}

= 17g

(D) 1 mol of $\mathrm{CO}$ = Molecular mass of $\mathrm{CO}$

Molecular mass of water = (Mass of carbon+Mass of oxygen)

= (12+16)

= 28g

Thus, option (B) is true i.e. 1 mole ${\mathrm{CO}}_2$ would weigh most.