Question

How many molecules of H2O are in 8.54 moles of H2O?

Select one:
a. 5.14 * 10^24 molecules H2O
b. 2.86 * 10^23 molecules H2O
c. 6.02 * 10^23 molecules H2O
d. 5.14 * 10^23 molecules H2O

Answer 1

5.14 x 10^24 molecules of H2O.

Step-by-step explanation:

just took the test

Answer 2

`\boxed {\boxed {\sf A. \ About \ 5.14 *10^(24) \ molecules \ H_2O}}`

Step-by-step explanation:

To convert from moles to units, we must use Avogadro's Number: 6.022 * 10²³

This tells us the number of units (molecules of water in this problem) in 1 mole of a substance (water). We can use it as a ratio or fraction.

`(6.022 *10^(23) \ molecules \ H_2O)/(1 \ mol \ H_2 O)`

Now, we can multiply this fraction by the moles of water (8.54) given.

`8.54 \ mol \ H_2O*(6.022 *10^(23)\ molecules \ H_2O)/(1 \ mol \ H_2 O)`

When we multiply, the moles of water will cancel out.

`8.54 *(6.022 \ molecules \ H_2O)/(1 \ )`

Since the fraction has a 1 as a denominator, we can remove it. The problem will be a simple multiplication problem.

`8.54*6.022 \ molecules \ H_2O`

`5.142788*10^(24) \ molecules \ H_2O`

The original measurement of 8.54 has 3 significant figures (8, 5, and 4). Therefore, we must round our answer to 3 sig figs, which is the hundredth place in this case.

The 2 in the thousandth place tells us to leave the 4 in the hundredth place.

`5.14 *10^(24) \ molecules \ H_2 O`

There are about 5.14*10²⁴ molecules of water in 8.54 moles.