I believe the answer is A (it was on another Brainly question as well).
If they're different sizes and densities, you are able to separate the substances.
Measure how much water has gone in, so you know the concentration.
The reaction between Na2S and CuSO4 will give us the balanced chemical reaction of,
Na2S + CUSO4 --> Na2SO4 + CuS
This means that for every 78g of Na2S, there needs to be 159.6 g of CuSO4. The ratio is equal to 0.4887 of Na2S: 1 of CuSO4. Thus, for every 12.1g of CuSO4, we need only 5.91 g of Na2S. Thus, there is an excess of 9.58 g of Na2S. The answer is letter C.
The standard temperature is 0c.
the standard pressure is 1atm.
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