Math word problem help please...?

Question

please help me with these word problems. show ur work thank you!!!!

1. A lab has 60 cubic centimeters (cc) of a solution that is 40% HCI acid. How many cc of a 15% solution of HCI acid should be mixed with the 60 cc if 40% HCI acid to obtain a solution of 25% HCI? How much of the 25% solution is there?

2. How much water should be added to 64 ounces of a 10% salt solution to make a 2% salt solution.

Answer 1

lazy

Answer 2

Hi,

1. A lab has 60 cubic centimeters (cc) of a solution that is 40% HCI acid. How many cc of a 15% solution of HCI acid should be mixed with the 60 cc if 40% HCI acid to obtain a solution of 25% HCI? How much of the 25% solution is there?

%(cm) + %(cm) = %(cm)

40(60) + 15x = 25(x + 60)

2400 + 15x = 25x + 1500

900 = 10x

90 = x

Add 90 cm of 15% HCl solution to make 150 cm of 25% solution <==ANSWER

2. How much water should be added to 64 ounces of a 10% salt solution to make a 2% salt solution.

%H2O(cm) + %H20(cm) = %H2O(cm)

100x + 90(64) = 98(x + 64)

100x + 5760 = 98x + 6272

2x = 512

x = 256 ounces

Add 256 ounces of water to make the 2% salt solution. <==ANSWER

I hope that helps!! :-)

Answer 3

The equation you use is

(% of solutions mixed)*(cc's of solution)=(total cc's)*(final %)

so for #1...

(x cc's)*(.15)+(60cc's)*(.40)= (x+60)*(.25)   Multiply and distribute

.15x+24=.25x+15                                     Subtract

9=.10x

90=x

#2 is the same except you gotta know that water is a 0% concentration.

(x ounces)*(0%)+(64 ounces)(.10)=(x+64)(.02)

6.4=.02x+1.28

5.12=.02x

x=256.

Hope this helps!

Answer 4

haha this isn't maths, its molecular chemistry, this is a mole equation.

you need to use your periodic table to work out how much of each is need.

the equation to use for solid is. moles = Weight/Relative Atomic Mass

for liquid. moles = volume x concentration/1000

for gas, moles = volume/24