A concentration converter

You will write three functions that a laboratory could use every day. One turns a bottle label into a molarity. One turns a molarity into a molality. One finds ppm.

The idea. Take a convenient amount of solution. Use the density to turn its mass into a volume. Then each measure is moles divided by the right quantity.

Your tasks.

1. Complete molarity_from_percent(percent, molar_mass, density) for a solution that is percent grams of solute in 100 g of solution.
2. Complete molality_from_molarity(molarity, molar_mass, density). Take 1 L of solution.
3. Complete ppm(solute_mg, solution_kg).