Question

How many mL of water must be added to 500 mL of alcohol to prepare a 40% v/v solution?

Answer 1

Respuesta:

This is a dilution problem, so we can use the dilution formula:

¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

∣

∣

a

a

c

1

V

1

=

c

2

V

2

a

a

∣

∣

−−−−−−−−−−−−−−−

c

1

=

70

%

;

V

1

=

300 mL

c

2

=

40

%

;

V

2

=

?

V

2

=

V

1

×

c

1

c

2

=

300 mL

×

70

%

40

%

=

525 mL

Thus, you would add 225 mL of water to 300 mL of 70 % alcohol, and you would get 525 mL of 40 % alcohol.

Check:

300 mL of 70 % alcohol contains 210 mL of alcohol, and 525 mL of 40 % alcohol contains 210 mL of alcohol.