Question

In the chemistry lab, a student makes a potassium hydroxide (KOH) solution by adding 40 grams of KOH to 500 mL of water. To check for understanding of solutions, the teacher asks the student to answer the following questions about the solution they have prepared. (Answer each question)Which substance is the solvent in your solution?Which substance is the solute in your solution?Calculate the molarity of your solution (show your work).The next step in the lab procedure is to dilute the concentration to 1.0 M. What volume of solvent should be added to the solution to dilute it to the proper 1.0 M concentration? (Show your work).

Answer 1

Since KOH dissolves in water so KOH is solute while water is solvent.

`Molarity\text{ = }\frac{moles\text{ of solute}}{volume\text{ of solution in ml}}\text{ * 1000}`

Now, we need to calculate moles of solute (KOH)

`Moles\text{ of KOH =}\frac{given\text{ mass of KOH}}{molar\text{ mass of KOH}}`
`=\text{ }(40)/(56)=0.714`
`So,\text{ Molarity = }(0.714)/(500)*1000=\text{ 1.428 mol/L}`

Now, we need to dilute the solution, so we will use molarity equation for dilution which is M1V1 = M2V2

Here, M1= 1.428 M; V1= 40 ml; M2 = 1 M; we need to find V2

`1.428\text{ * 40 = 1 * V2}`Therefore, V2 = 57.12 ml