Given that mass of an atom of helium gas is `6.68 xx 10^(-27) kg`. Calculate Avogadro's number. Molecular weight of He = 4.

Explanation

To calculate Avogadro's number using the given data, we can follow these steps:

### Step 1: Convert the mass of one atom of helium from kg to grams.
Given:
- Mass of one atom of helium = \( 6.68 \times 10^{-27} \) kg

To convert kg to grams, we use the conversion factor \( 1 \text{ kg} = 1000 \text{ g} \):
\[ \text{Mass of one atom of He in grams} = 6.68 \times 10^{-27} \text{ kg} \times 1000 \text{ g/kg} = 6.68 \times 10^{-24} \text{ g} \]

### Step 2: Understand the relationship between molecular weight and Avogadro's number.
The molecular weight of helium (He) is given as 4 g/mol. This means that 4 grams of helium contains Avogadro's number (\( N_A \)) of atoms.

### Step 3: Use the formula to calculate Avogadro's number.
Avogadro's number can be calculated using the formula:
\[ N_A = \frac{\text{Molecular weight}}{\text{Mass of one atom}} \]
Substituting the values we have:
\[ N_A = \frac{4 \text{ g/mol}}{6.68 \times 10^{-24} \text{ g}} \]

### Step 4: Perform the calculation.
Now we perform the division:
\[ N_A = \frac{4}{6.68 \times 10^{-24}} \approx 5.99 \times 10^{23} \text{ atoms/mol} \]

### Final Result:
Thus, Avogadro's number is approximately:
\[ N_A \approx 5.99 \times 10^{23} \text{ atoms/mol} \]

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