Question

mathxl for school: practice & problem solving (lms graded)
part 2 of 2
a scientist is determining the mass of 24,000 molecules of oxygen.
use this to answer parts a and b.
the mass of one oxygen = 5.3×1

1. how many significant digits should be in the solution?

there should be 2 significant digits in the solution.
(type a whole number.)

1. express the mass of 24,000 molecules of oxygen in scientific notation.

grams
(type your answer using the appropriate number of significant digits. type your answer in scientific notation using the appropriate symbol from the math palette for multiplication.)

Explanation:

Step1: Identify mass of one oxygen

The mass of one oxygen molecule is given as $5.3\times 10^{-23}$ grams.

Step2: Calculate mass of 24000 molecules

Multiply the mass of one molecule by the number of molecules. $24000\times(5.3\times 10^{-23})=(2.4\times 10^{4})\times(5.3\times 10^{-23})$.
Using the rule of exponents $a^m\times a^n=a^{m + n}$, we have $(2.4\times5.3)\times10^{4+( - 23)} = 12.72\times10^{-19}$.

Step3: Adjust to scientific - notation and significant digits

In scientific notation, we need a number between 1 and 10. So, $12.72\times10^{-19}=1.272\times 10^{-18}$.
Since we are supposed to have 2 significant digits, we round $1.272$ to $1.3$. So the mass is $1.3\times 10^{-18}$ grams.

Answer:

$1.3\times 10^{-18}$ grams