Question

the solubilities of three salts in water are shown in the graph. for each salt, determine how much will remain undissolved if 300 g is mixed into a liter of pure water at 40 °c. one significant figure is sufficient in each answer.

Explanation:

Step1: Read solubility from graph

From the graph, at 40°C, the solubility of $Pb(NO_3)_2$ is about 700 g/L, solubility of KI is about 400 g/L and solubility of $K_2Cr_2O_7$ is about 200 g/L.

Step2: Calculate undissolved amount for $Pb(NO_3)_2$

Since 700 g/L > 300 g/L, all 300 g of $Pb(NO_3)_2$ will dissolve. Undissolved amount = 0 g.

Step3: Calculate undissolved amount for KI

Amount added = 300 g, solubility = 400 g/L. All 300 g will dissolve. Undissolved amount = 0 g.

Step4: Calculate undissolved amount for $K_2Cr_2O_7$

Amount added = 300 g, solubility = 200 g/L. Undissolved amount = 300 - 200= 100 g.

Answer:

$Pb(NO_3)_2$: 0 g
KI: 0 g
$K_2Cr_2O_7$: 100 g