Final answer:
The mass of undissolved copper sulfate is 28.56g.
Step-by-step explanation:
The solubility of copper sulfate at 20°C is 32g/100g water.
If 42g of copper sulfate is added to 100g of water, we can calculate the mass of undissolved copper sulfate by subtracting the amount that dissolved from the total amount added.
First, we need to determine how much copper sulfate actually dissolved.
Using the solubility of 32g/100g water, we can set up a proportion: 32g/100g water = xg/42g copper sulfate.
Solving for x, we find that x = (32g/100g water) * (42g copper sulfate) = 13.44g.
Therefore, 13.44g of copper sulfate dissolved.
Finally, we can calculate the mass of undissolved copper sulfate by subtracting the amount dissolved from the total amount added:
42g copper sulfate - 13.44g = 28.56g.