Question

A 15.7 g sample of KBr is dissolved in water to give 6.50 \times 10^26.50×10 2
mL of solution. The concentration of the solution is:
0.203 MM 0.640 MM
0.0203 MM
0.0640 MM

Answer 1

Explanation:

For starters, convert the mass of potassium bromide to moles by using the molar mass of the compound.

15.6

g

⋅

1 mole KBr

119.002

g

=

0.1311 moles KBr

Now, in order to find the molarity of the solution, you need to figure out how many moles of solute are present for every

1 L

of solution.

You already know that

1.25 L

of solution contain

0.1311

moles of potassium bromide, the solute, so all you have to do now is to use this known composition as a conversion factor to go from

1 L

of solution to number of moles of solute.

1

L solution

⋅

0.1311 moles

1.25

L solution

=

0.10488 moles KBr

Since this represents the number of moles of solute present in

1 L

of solution, you can say that the molarity of the solution is equal to

molarity = 0.105 mol L

−

1

−−−−−−−−−−−−−−−−−−−−−−

Answer 2

Answer:

0.0203

Explanation: