Dr. Slotsky Chemistry II Molarity Problems Worksheet with handwritten solutions and notes.

You're working on a Molarity Problems Worksheet from Dr. Slotsky’s Chemistry II class.

The key formula you need is:

> M = n / V

Where:
- M = Molarity (in mol/L or M)
- n = number of moles of solute
- V = volume of solution in Liters

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Problem 1:

> What is the molarity of a 0.20 liter solution containing 0.50 moles of NaCl?

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Step-by-step Solution:

We are given:
- n = 0.50 moles of NaCl
- V = 0.20 liters

Plug into the formula:

> M = n / V = 0.50 mol / 0.20 L

> M = 2.5 mol/L

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✔ Final Answer: 2.5 M

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Explanation:

Molarity tells us how concentrated a solution is — specifically, how many moles of solute are dissolved per liter of solution.

Here, you have 0.50 moles of NaCl dissolved in just 0.20 liters of solution. Since that’s less than 1 liter, the concentration is higher than if it were in 1 liter — and indeed, 0.50 ÷ 0.20 = 2.5, meaning there are 2.5 moles of NaCl per liter.

This makes sense — if you had 0.50 moles in 1 liter, it would be 0.50 M. But since you’re squeezing the same amount into only 0.20 L (which is 1/5 of a liter), the concentration becomes 5 times higher → 0.50 × 5 = 2.5 M.

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✔ Remember: Always ensure volume is in Liters, not mL! If you had been given mL, you’d convert by dividing by 1000.

Let me know if you want help with the next problems too — I can walk you through them one by one!