Question

Recorded data:
Before$:$ $CuO+$porcelain boat$=62.869g$
$CaC{l}_2+$U-tube$=80.483g$
After:Porcelain boat$+$contents $=54.869g$
$CaC{l}_2+U$-tube$=89.483g$
Reactions:$Zn\left(s\right)+2HCl\left(aq\right)\to ZnC{l}_2\left(aq\right)+H_2\left(g\right)$ then $H_2\left(g\right)+CuO\left(s\right)\to H_{2}O\left(g\right)+Cu\left(s\right)$
What conclusion can you draw after the completion of this experiment?

• A. Hydrogen diffuses faster than oxygen
• B. Hydrogen is lighter than oxygen
• C. The molar mass of oxygen is $32g/mol$.
• D. Water is a triatomic molecule with polar characteristics
• E. Water is formed from hydrogen and oxygen in a ratio of $1:8$, by mass.

Answer 1

The correct option is E Water is formed from hydrogen and oxygen in a ratio of $1:8$, by mass.

Mass of $CaC{l}_2+U$ tube $=80.483g$
Mass of $CaC{l}_2+U$ tube $+H_{2}O=89.483g$.
Mass of water $=89.483-80.483=9g$
The molar mass of water is 18 $g/mol$
9 $g$ water corresponds to $\frac{9g}{18g/mol}=0.5mol$.
1 $mol$ of $H_2$ gives 1 $mol$ of $H_{2}O$
0.5 $mol$ of $H_2$ will give 0.5 $g$ of $H_{2}O$
The molar mass of $H_2$ is 2 $g/mol$.
Mass of $H_2=2g/mol\times 0.5mol=1g$
Hence, 1 gram of hydrogen were used in the formation of the water as product.
Mass of $CuO+$ porcelain boat $=62.869g$
Mass of $Cu+$ porcelain boat $=54.869g$
Mass of oxygen $=62.869-54.869=8g$
Hence, water is formed from hydrogen and oxygen in a ratio of 1:8, by mass.