Question

Recorded data:
Before$:$ $CuO+$porcelain boat$=62.869$g
$CaC{l}_2+$U-tube$=80.483$g
After:Porcelain boat$+$contents $=54.869$g
$CaC{l}_2+$U-tube$=89.483$g
Reactions:$Zn\left(s\right)+2HCl\left(aq\right)\to ZnC{l}_2\left(aq\right)+H_2\left(g\right)$ then $H_2\left(g\right)+CuO\left(s\right)\to H_{2}O\left(g\right)+Cu\left(s\right)$
Which of the following is an observation rather than a conclusion?

• A. A substance is an acid if it changes litmus paper from blue to red.
• B. A gas is lighter than air if it escapes from a bottle left mouth upward
• C. The gas $H_2$ forms an explosive mixture with air
• D. Air is mixed with hydrogen gas and ignited; it explodes
• E. A liquid oil is immiscible with water because it separates into a layer above the water

Answer 1

The correct option is D Air is mixed with hydrogen gas and ignited; it explodes

As the weight of the $CuO$ including porcelain boat decreases and weight of $CaC{l}_2$ including U tube increases infers that the $H_2$ gas liberated from $Zn$ and $HCl$ reacts with $CuO$ to form water and increases the weight of $CaC{l}_2.i.e.$ it explodes with oxygen present in air to form water.