Question

How many grams of KBr are dissolved in 92.7 mL of a 0.955 M solution? Show your work.

Answer 1

10.5g of KBr

Step-by-step explanation:

molarity = moles of solute / litres of solution

we are given the volume of the solution in milliliters but the formula uses litres so we have to convert

to convert to liters we divide the number of milliliters by 1000 ( because 1 liter has 1000 milliliters. )

so liters of solution = 92.7/1000 = 0.0927 L

we can now plug in what we are given and solve for moles of solute

recall molarity = moles of solute / litres of solution

molarity = 0.955M and liters of solution = 0.0927L

so
`0.955M=(moles.of.solute)/(0.0927L)`

multiply both sides by 0.0927

we're left with moles of solute = 0.0885285 moles

Finally we must convert moles to grams

Molar mass of KBr = 39.0983 + 79.904 = g/mol

Using dimensional analysis we get
`\frac{0.0885285molKBr}{} *(119.002g)/(1molKBr)`

the mol KBr cancel out on both sides and we get
`0.0885285 *119.002g` which is equal to 10.5g (rounded)

So we can conclude that 10.5g of KBr is dissolved in 92.7mL of a 0.955M solution.