Solve the problem. Express your answer in scientific notation, and round to one decimal place.
-The mass of an electron is approximately $9.11 \times 10 ^ { - 28 }$ grams. Find the mass of $813,000,000$ electrons.
A) $7.4 \times 10 ^ { - 18 }$ grams
B) $7.4 \times 10 ^ { - 20 }$ grams
C) $7.4 \times 10 ^ { - 19 }$ grams
D) $7.4 \times 10 ^ { - 17 }$ grams

Question

Quizplus · Accepted Answer

To find the mass of $813,000,000$ electrons, we need to multiply the mass of one electron ($9.11 \times 10 ^ { - 28 }$ grams) by the number of electrons.
$$mass = (9.11 \times 10 ^ { - 28 }) \times (813,000,000)$$
Using a calculator, we get:
$$mass = 7.40843 \times 10 ^ { - 19 }$$
Rounding to one decimal place gives:
$$mass \approx 7.4 \times 10 ^ { - 19 }$$
Therefore, the answer is choice C.

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