Answer :
ANSWER
The mass of the solute is 8.2 grams
EXPLANATION
Given that;
The volume of the solute is 125mL
The molarity of the solution is 0.25M
Follow the steps below to find the mass of the solute
Note; the solute is Ba(NO3)2
Step 1; Convert the volume of the solution to L
Recall, that 1 mL is equivalent to 0.001L
Let v represent the volume of the solution in L
[tex]\begin{gathered} \text{ 1mL }\rightarrow\text{ 0.001L} \\ \text{ 125mL }\rightarrow\text{ vL} \\ \text{ cross multiply} \\ \text{ 1mL}\times vL\text{ }=\text{ 125mL }\times\text{ 0.001L} \\ \text{ Isolate vL} \\ \text{ vL}=\text{ }\frac{125\cancel{mL}\times0.001L}{1\cancel{mL}} \\ \text{ v }=\text{ 0.125L} \end{gathered}[/tex]Hence, the volume in Liters is 0.125L
Step 2; Find the number of moles of the solute using the below formula
[tex]\text{ n }=\text{ cv}[/tex][tex]\begin{gathered} \text{ n }=\text{ 0.25 }\times\text{ 0.125} \\ \text{ n }=\text{ 0.03125 mole} \end{gathered}[/tex]STEP 3: Find the mass of the solute using the formula below
[tex]\text{ Mole }=\text{ }\frac{\text{ mass}}{\text{ molar mass}}[/tex]Recall, that the molar mass of Ba(NO3)2 is 261.337 g/mol
[tex]\begin{gathered} \text{ 0.03125 }=\frac{mass}{261.337} \\ \text{ Cross multiply} \\ \text{ mass }=\text{ 0.03125 }\times\text{ 261.337} \\ \text{ mass }=\text{ 8.2 grams} \end{gathered}[/tex]Hence, the mass of the solute is 8.2 grams