Question

How many moles are in 1.806 x 1024 molecules of bromine?

Answer 1

`\boxed {\boxed {\sf About \ 2.999 \ moles \ of \ bromine}}`

Step-by-step explanation:

To convert from moles to molecules, we must use Avogadro's Number.

`6.022*10^(23)`

This tells us the number of particles (atoms, molecules, ions, etc) in 1 mole. In this problem, the particles are molecules of bromine in 1 mole of bromine.

`6.022*10^(23) \ molecules \ Br / 1 \ mol \ Br`

1. Convert from moles to molecules

Use Avogadro's number as a fraction or ratio.

`(6.022 *10^(23) \ molecules \ Br)/(1 \ mol \ Br)`

Multiply this fraction by the given number of bromine molecules.

`1.806 *10^(24) molecules \ Br *(6.022 *10^(23) \ molecules \ Br)/(1 \ mol \ Br)`

Flip the fraction so the molecules of bromine can cancel out.

`1.806 *10^(24) \ molecules \ Br* (1 \ mol \ Br)/(6.022 *10^(23) \ molecules \ Br)`

`1.806 *10^(24) * (1 \ mol \ Br)/(6.022 *10^(23))`

Multiply and condense the expression into 1 fraction.

`(1.806 *10^(24) \ mol \ Br)/(6.022 *10^(23) )`

Divide.

`2.999003653 \ mol \ Br`

2. Round

The original measurement, 1.806*10^24 has 4 significant figures (1, 8, 0, and 6). We must round our answer to 4 sig figs. For the answer we found, that is the thousandth place.

`2.999003653 \ mol \ Br`

The 0 in the ten-thousandth place tels us to leave the 9 in the thousandth place.

`\approx 2.999 \ mol \ Br`

There are about 2.999 moles of bromine in 2.806 *10^23 molecules.

Answer 2

2.999 mol Br

General Formulas and Concepts:

Math

Pre-Algebra

Order of Operations: BPEMDAS

1. Brackets
2. Parenthesis
3. Exponents
4. Multiplication
5. Division
6. Addition
7. Subtraction

• Left to Right

Chemistry

Atomic Structure

• Using Dimensional Analysis
• Avogadro's Number - 6.022 × 10²³ atoms, molecules, formula units, etc.

Step-by-step explanation:

Step 1: Define

1.806 × 10²⁴ molecules Br

Step 2: Identify Conversions

Avogadro's Number

Step 3: Convert

`\displaystyle 1.806 \cdot 10^(24) \ molecules \ Br((1 \ mol \ Br)/(6.022 \cdot 10^(23) \ molecules \ Br) )` = 2.999 mol Br

Step 4: Check

We are given 4 sig figs. Follow sig fig rules and round.

Our final answer is already in 4 sig figs, so there is no need to round.