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6. How does the mass of Copper (II) oxide change when it is heated in Hydrogen and in Oxygen
Mass after heating in Hydrogen , ?Mass after heating in Oxygen
A) decrease ,?decrease
B) decrease , unchanged
C) unchanged , ?decrease
D) unchanged , ?unchangedAns: B
What are your thoughts?
This is a pretty easy question. Wonder how come no students attempted on
this question.
CuO(s) are reduced back to copper with hydrogen gas:
CuO(s) + H2(g) Cu(s) + H2O(g)
As such, there is a decrease in the mass of CuO.
Note:
Hydrogen gas are common reducing agent. In this case, it has reduced CuO
from Cu(2+) to Cu(0).
No reaction between the CuO and Oxygen gas upon heating. Thus the mass
of CuO remains unchanged.
Hope this helps,
Sean