Question

1.36 .

What is the initial volume, in milliliters, needed to prepare each of the following diluted solutions?1) 150 mL of 6.0 % (m/v) glucose from 25 % (m/v) glucose

1) 150 mL of 6.0 % (m/v) glucose from 25 % (m/v) glucose

2) 40.0 mL of 3.0 % (m/v) CaCl2 from 10 % (m/v) CaCl2

3) 100. mL of 5.50 MH2SO4 from 16.0 MH2SO4

Answer 1

We need to apply dilution law, which is based on the mass conservation principle

initial mass = final mass

this apply for moles as weel ( if there is no reaction, which is the case )

mol of A initially = mol of A finally

or, for this case

moles of A in stock = moles of A in diluted solution

Recall that

mol of A = Molarity of A * Volume of A

then

moles of A in stock = moles of A in diluted solution

Molarity of A in stock * Volume of A in stock = Molarity of A in diluted solution* Volume of A in diluted solution

Now, substitute known data

Q1

C1V1 = C2V2

25*V1 = 150*6

V1 = 150*6/25

V1 = 36 mL

q2

C1V1 = C2V2

10*V1 = 3*40

V1 = 3*40/10

V1 = 12 mL

Q3

C1V1 = C2V2

16*V1 = 5.5*00

V1 = 5.5*100/16

V1 = 34.375 mL