Question

how many molecules of vitamin a, c₂₀h₃₀o, are in a sample that contains 4.0 × 10²² atoms c?
3.0 × 10²¹ molecules of c₂₀h₃₀o
2.0 × 10²¹ molecules of c₂₀h₃₀o
1.0 × 10²¹ molecules of c₂₀h₃₀o
6.0 × 10²¹ molecules of c₂₀h₃₀o

Explanation:

Step1: Determine C atoms per molecule

Each \( \text{C}_{20}\text{H}_{30}\text{O} \) molecule has 20 C atoms.

Step2: Calculate molecules from C atoms

Use the ratio: \( \text{Molecules of } \text{C}_{20}\text{H}_{30}\text{O} = \frac{\text{Atoms of C}}{20} \)
Substitute \( \text{Atoms of C} = 4.0 \times 10^{22} \):
\( \text{Molecules} = \frac{4.0 \times 10^{22}}{20} = 2.0 \times 10^{21} \)

Answer:

B. \( 2.0 \times 10^{21} \) molecules of \( \text{C}_{20}\text{H}_{30}\text{O} \)