Calculating moles - how do I work out moles when I know something is 5% w/v in 12cm3 of solution?

Question

If I have 5% w/v of a solution of silver nitrate and I use 12 cm3 of it, how do I work out how many moles I have used? I'd like to know the method, rather than the answer please!

Help is greatly appreciated :)

Answer 1

You have to know the density of the solution.
Would you be so Kind to tell me the density?
I will answer

Answer 2

Once you get the density as mentioned above, the rest is straightforward.

Since D =M/V, you can solve for the mass by plugging in the density and the 12 cm3. Since it is only only 5% w/v, multiply your total mass by 5% to get the grams of AgNO3. Then you can calculate moles in the usual way

Answer 3

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Answer 4

Always remember that one mole = mass of solution (g)/Molecular weight

In this case, Molecular weight of Silver Nitrate = AgNO3=169.87

5%w/v means = 5 gram of solution in 100 ml = 5g/100 ml

1 ml =1 cm3, hence 12cm3=12 ml

Therefore in 12cm3 of solution you have 12/100 x 5 g = 0.6 gram of silver nitrate

Now after you have obtained the mass of silver nitrate in the 12cm3 of volume you use, you can calculate the moles using the above formula

moles = mass (g)/molecular weight = 0.6 g/168.87 = 0.0035 moles