Question

What is the mass in gram of 1 atom of an element if its atomic mass is 10 u?

• A. $2.06056\times10^{-22}\text{ g}$
• B. $1.66056\times10^{-23}\text{ g}$
• C. $1.06056\times10^{-24}\text{ g}$
• D. $3.66056\times10^{-25}\text{ g}$

Hint:

Logic Tip: $1 \text{ u}$ is precisely the reciprocal of Avogadro's number ($1 / N_A$) in grams. $1 / 6.022 \times 10^{23} \approx 1.66 \times 10^{-24} \text{ g}$. Multiplying this by 10 simply shifts the decimal point by one place, making the exponent $-23$.

Answer 1

The Correct Option is B

Concept:
The unified atomic mass unit ($u$ or amu) is defined as one-twelfth of the mass of an unbound neutral atom of carbon-12 at rest. The conversion factor between unified atomic mass units and grams is a fundamental physical constant. $$1 \text{ u} = 1.66056 \times 10^{-24} \text{ g}$$
Step 1: Identify the given atomic mass.
We are given the atomic mass of a single atom of the element: $$\text{Mass of 1 atom} = 10 \text{ u}$$
Step 2: Convert the mass from unified atomic mass units to grams.
Multiply the given mass by the conversion factor: $$\text{Mass in grams} = 10 \text{ u} \times \left(1.66056 \times 10^{-24} \frac{\text{g{\text{u\right)$$ $$\text{Mass in grams} = 1.66056 \times 10^{-23} \text{ g}$$