concentrate..u can save me!?

Question

40 ml 3% H2O2 = 3.0% H2O2
20 ml 3% H2O2 + 20 ml distilled water = 1.5% H2O2
10 ml 3% H2O2 + 30 ml distilled water = 0.75% H2O2
5 ml 3% H2O2 + 35 ml distilled water = 0.38% H2O2
40 ml distilled water = 0.0% H2O2


someone tell me how did they come up with 1.5%, 0.75% and 0.38%...i mean how to calculate this?thanks.

but what is M1V1=M2V2 ???

Answer 1

40 ml 3% H2O2 contains 3% H2O2 which is 1.2ml
.
20 ml 3% H2O2 means it has 20*3%= 0.6ml H2O2
so 20ml 3%H2O2 + 20ml distilled water contains 0.6ml H2O2 in 40ml. So, 0.6/40=1.5%H2O2

similarly, 10ml 3%H2O2 has 0.3ml H2O2.
So 10ml 3% H2O2 +30ml dist Water makes a 40ml solution with 0.3 ml H2O2 making it 0.3/40=0.75%H2O2 solution.

Same steps for the 5ml case.

Answer 2

it's a dilution problem

M1V1=M2V2. here just use percents as the concentration and the rest is easy

Answer 3

srry dont know