You combine 0.01500 moles of solid NaCl with 150 mL of water. Your lab partner combines 6.0 mL of his 2.5 M solution with 144 mL of water.
Work Step by Step
You: To create 0.150 L of 0.10 M solution, we need $0.150*0.10=0.0150$ moles of NaCl. We then add 150 mL of water to create a 150 mL solution with 0.10 M. Lab Partner: We apply the formula $M_1V_1=M_2V_2$ to solve how much of the 2.5 M solution your lab partner should use. Let V be the amount in liters that your lab partner needs to make the desired solution: $$2.5*V=0.150*0.1 \Rightarrow V=0.006$$ Therefore, we need to add 6 mL of stock 2.5 M solution as well as 144 mL of water to create the 150 mL solution with 0.10 molarity.