# I have 2oz concentrated 40% aqueous solution, I want to dilute it 10% , How I dilute it ??? Please I need you kind help. Thank you

##### 1 Answer

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#### Explanation:

The idea with dilution calculations is that every time you're diluting a solution, the number of moles of *solute* will remain **constant**.

In your case, you start with a

#color(blue)("%m/m" = "mass of solute"/"mass of solution" xx 100)#

A **for every**

In your case, the

#2color(red)(cancel(color(black)("oz solution"))) * "40 oz solute"/(100color(red)(cancel(color(black)("oz solution")))) = "0.80 oz solute"#

Now, when you dilute this olution, the mass of solute **remains unchanged**. Let's say that you add

#10% = (0.80color(red)(cancel(color(black)("oz"))))/((0.80 + x)color(red)(cancel(color(black)("oz")))) xx 100#

Solve this equation for

#10 * (0.80 + x) = 0.80 * 100#

#8 + 10x = 80#

#10x = 72 implies x = 72/10 = 7.2#

So, if you add