Question

From the recorded data:
Weight of U-tube $=20.36$g
Weight of U-tube and calcium chloride before $=39.32$g
Weight of U-tube and calcium chloride after $=57.32$g
Weight of boat and contents(copper oxide)before $=30.23$g
Weight of boat and contents after $=14.23$g
Weight of boat $=5.00$g
Determine the ratio of the mass of water formed to the mass of hydrogen used in the formation of water?

• A. $1:8$
• B. $1:9$
• C. $8:1$
• D. $9:1$
• E. $8:9$

Answer 1

Answer: (D)

$9:1$

Weight of U-tube and calcium chloride before..............39.32g
Weight of U-tube and calcium chloride after................57.32g
Mass of water formed $=57.32-39.32=18g$

Weight of boat and contents(copper oxide)before...............30.23g
Weight of boat and contents after...................14.23g
Mass of oxygen reacted $=30.23-14.23=16g$
Molar masses of oxygen, water and hydrogen are 16 g/mol, 18 g/mol and 2 g/mol respectively.
Number of moles of oxygen $=\frac{16}{16}=1$ mole.
$2H_2+O_2\to 2H_{2}O$
2 moles of hydrogen react with 1 mole of oxygen.
Number of moles of hydrogen $=2\times 1=2$
Mass of hydrogen $=2mol\times 2g/mol=4g$
2 moles of water are formed from 2 moles of hydrogen.
Mass of water formed $=2mol\times 18g/mol=36g$
The ratio of the mass of water formed to the mass of hydrogen used in the formation of water is $36:4$ or $9:1$