Sterile water is added to 2 grams of sodium chloride to make 100ml of solution.
a. whay is the concentration (stated as percent)?
b. is the solution hopotonic or hypertonic to human cells?

2 % of NaCl concentration

The solution is hypertonic to human cells

Explanation:

% Concentration = (g solute / g solution) * 100

Therefore

% Concentration of NaCl = (2 g NaCl/ 100 g solution) * 100

The concentration of the solution equals 2 %

Isotonic solutions for human red cells have a concentration of 0.9 % of NaCl.  A concentration of 2 % of NaCl is above 0.9 %, so the solution is hypertonic, since you have more concentration of solute (NaCl) outside the cell, than inside the cell ( inside the side you have only 0.9 % NaCl). So the cell will shrink.