First you didn't say what units you want for the concentration. That can be g/L, g/mL, kg/L, mols/L, equivalents/L, etc. .
MOST posts here want mols/L = M so that is what I will do.
Molarity of a solution is the number of moles/liter of solution or M = mols/L.
You are not given mols in the problem. You are given grams so you much convert that to mols.
You do that this way. mols = grams/molar mass
grams in the problem is 28. Molar mass NH3 is 14+3 = 17 so
mols = 28/17 = 1.647. To two places that rounds off to 1.6 mols.
Then you plug into M = mols/L of solution.
mols from above is 1.6.
L of solution is 500 mL or 0.500 L so
M = 1.6/0.500 = ? M
This is picky but let me point out something in the problem. The problem says the NH3 is dissolved in 500 mL of water. BUT, and this is a big but, the definition of M is mols/L OF SOLUTION and that is NOT the same as dissolving in 500 mL of water. That 500 mL of water will expand and will NOT be 500 mL OF SOLUTION. So the problem should have said "assume the addition of NH3 does not change the volume" (or something like that) OR it should have given you some way to calculate the new volume. It's just a poorly worded question. But with the understanding that we assume no volume change then my solution above is correct. Another possibility is that you want the concentration is molality (not molarity) in which case the problem is worked another way.
28g of NH3 is dissolved in 500mL of water. What is the concentration of the resulting solution?
(I do not understand how to solve this. If you can explain, that'd be great!)
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Also, dissolving NH3 into water creates NH4OH. So, technically the answer will be wrong. However, conceptually and mathematically the answer is correct.
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