Question

How many moles of urea is present in 250 ml of 0.2 M solution of it?

• A. 0.03
• B. 0.04
• C. 0.05
• D. 0.06

Hint:

A common mistake in molarity calculations is forgetting to convert the volume to liters. Always ensure your units are consistent before multiplying. Molarity is always in moles per liter.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
We are given the molarity and volume of a urea solution and asked to calculate the number of moles of urea.

Step 2: Key Formula or Approach:
Molarity (M) is defined as the number of moles of solute per liter of solution.
\[ \text{Molarity (M)} = \frac{\text{moles of solute}}{\text{Volume of solution in Liters (L)}} \]
We can rearrange this formula to solve for the moles of solute:
\[ \text{moles} = \text{Molarity} \times \text{Volume (L)} \]

Step 3: Detailed Explanation:
Given values are:
- Molarity = 0.2 M (which means 0.2 moles/liter)
- Volume = 250 ml
First, we must convert the volume from milliliters (ml) to liters (L):
\[ \text{Volume (L)} = 250 \text{ ml} \times \frac{1 \text{ L}}{1000 \text{ ml}} = 0.250 \text{ L} \]
Now, use the rearranged formula to calculate the number of moles:
\[ \text{moles} = 0.2 \frac{\text{mol}}{\text{L}} \times 0.250 \text{ L} \]
\[ \text{moles} = 0.05 \text{ mol} \]

Step 4: Final Answer:
There are 0.05 moles of urea present in the solution.