What mass of KCl would be needed to form a saturated solution if the KCl was dissolved in 200g of water at 80 C?

Attached we can observe the graph of solubility.

For KCl at 80 ° C, 50 g of KCl are required per 100 g of water.

We apply a simple rule of three, we have :

50 g KCl - - - - - - - - - > 100 g water

X - - - - - - - - - - - - - - - - - - - - > 200 g water

X = 200 g water · 50 g KCl / 100 g Water

X = 100 g KCl

Therefore, 100 g of KCl is needed to obtain a mixture saturated with 100 g of water at a temperature of 80 ° C.