How many grams of NaCl (MW: 58.5 g/mol) is needed to prepare a 50mL solution of 0.7% NaCl? Show work.

Question

anonymous · Answer

Do you mean a solution of 0.7 M NaCl?

This all starts with the equation Molarity = mols/Litre

We want to know how many mol of NaCl we need to add to 50mL of water.

Rearrange the equation to mols = Molarity*Litre and calculate the required mols of NaCl... 
0.050*0.7 = 0.035mol of NaCl is needed for the solution.

Then we need to calculate the mass of 0.035mol of NaCl so times the mols by it's molar mass (which is given in the question as 58.5 g/mol).
0.035*58.5 = 2.0475grams.

Therefore, ~2 grams of NaCl is required.