I am having problems with this question, I do not know if I amanswering correctl

Question

I am having problems with this question, I do not know if I amanswering correctly...
The problem goes like this:

3 grams of NaCl in 100 grams of water.
density = 1.1 g/ml
a) find the molal concentration
b) find the molar concentration

What I did first is finding the number of moles of NaCl:
3gNaCl * 1mol/58.5g NaCl = 0.0513 moles NaCl

Then, I got the molal concentration by dividing the number of molesof NaCl and the mass of the water converted to kilograms:
m = 0.0513 / 0.1kg
= 0.513 m

Finally I tried to convert the molal concentration to a molarconcentration. I need to get the volume of the water using thisformula: v = mass/density.

If I try to get the mass like this:
0.513m NaCl * 58.5gNaCl/1 mole = 30g NaCl
30g NaCl + 100g Water = 130g total mass

I get 30 grams of NaCl but the problem says there is 3 grams ofNaCl, so I dont know whats wrong.. should I use 130g (100 +30) or 103 g (100 + 3) for the total mass. did I calculatethe molal concentration correctly?

Explanation / Answer

Ok, I already found out the answer to my question by looking to asimilar problem: 12.23p in the chemistry (9th) by chang book.

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