If 33.6 g of sodium chloride are dissolved in 125 g of water, what is the mass percent concentration (m/m) of  NaCl in the solution?

To calculate the mass percent concentration (m/m) of NaCl in the solution, you need to follow these steps:

1. First, you need to find the total mass of the solution. This is done by adding the mass of the sodium chloride (NaCl) to the mass of the water. In this case, that would be 33.6 g (NaCl) + 125 g (water) = 158.6 g (total mass of the solution).

2. Next, you calculate the mass percent concentration by dividing the mass of the solute (NaCl) by the total mass of the solution and then multiplying by 100 to get a percentage. So, (33.6 g / 158.6 g) * 100 = 21.2%.

So, the mass percent concentration (m/m) of NaCl in the solution is 21.2%.