An organic compound made of C, H and N contains 20% of nitrogen. Its molecular weight is

Options

A. 70
B. 140
C. 100
D. 65

Explanation

To find the molecular weight of the organic compound that contains 20% nitrogen, we can use the mass percent formula. Here’s a step-by-step solution:

### Step 1: Understand the Given Information
We know that the organic compound consists of Carbon (C), Hydrogen (H), and Nitrogen (N) and that it contains 20% nitrogen by mass.

### Step 2: Use the Mass Percent Formula
The mass percent formula states that:
\[ \text{Mass percent of an element} = \left( \frac{\text{Molar mass of the element}}{\text{Molecular weight of the compound}} \right) \times 100 \]
In our case, we are given the mass percent of nitrogen (N) as 20%.

### Step 3: Identify the Molar Mass of Nitrogen
The molar mass of nitrogen (N) is approximately 14 g/mol.

### Step 4: Set Up the Equation
Using the mass percent formula for nitrogen, we can set up the equation:
\[ 20 = \left( \frac{14}{\text{Molecular weight}} \right) \times 100 \]

### Step 5: Rearrange the Equation to Solve for Molecular Weight
Rearranging the equation gives us:
\[ \text{Molecular weight} = \frac{14 \times 100}{20} \]

### Step 6: Calculate the Molecular Weight
Now, we can perform the calculation:
\[ \text{Molecular weight} = \frac{1400}{20} = 70 \text{ g/mol} \]

### Final Answer
The molecular weight of the organic compound is **70 g/mol**.

---