## Empirical Formula

sarahtang4B
Posts: 132
Joined: Fri Sep 28, 2018 12:27 am

### Empirical Formula

So I came across some problems on the modules that asked for empirical formulas and I was confused on how to get atoms to be a whole ratio.

For example, if a ratio is 1 : 0.13 : 2.23, in this case, how do we multiply to get the ratio to be whole numbers, do we just multiply until both decimals are relatively close to a whole number?

What number do I multiply by?

thank you!

AhYeon_Kwon_2H
Posts: 48
Joined: Fri Sep 28, 2018 12:27 am

### Re: Empirical Formula

The best way of approaching this is to try to multiply the decimals by the smallest number possible.

For example, we can either multiply based on the 0.13 or the 2.23.
0.13 is close to 0.10, so we would theoretically multiply all the numbers by 10.
2.23 is close to 2.25, so we would theoretically multiply all the numbers by 4.

4 is the smaller number, so multiply the three numbers by 4 to get 4 : 0.52 : 8.92.
Since the middle number is still a decimal, multiply once again (this time by 2, since 0.52 is close to 0.50).

I think the final ratio should be 8 : 1 : 18.

The only issue I'm not sure on is whether 8.92 is high enough to be rounded to 9. If someone else could shed some light on that, that would be great! :)

yea-lyn pak_1G
Posts: 30
Joined: Fri Sep 28, 2018 12:18 am

### Re: Empirical Formula

I think the general rule was that if you're going to round, the rounded number should be within 5% of the original answer you got.

Bingcui Guo
Posts: 30
Joined: Fri Sep 28, 2018 12:19 am

### Re: Empirical Formula

I think you can just divide all the other bigger numbers by the smallest one and round them to by the significant figure rules. Cuz I think in this case, some roundoff is acceptable

Danielle_Gallandt3I
Posts: 70
Joined: Fri Sep 28, 2018 12:24 am

### Re: Empirical Formula

In this case, another way of getting to that answer would be to take the smallest number in that ratio and divide all numbers within the ratio by that number. When you do that you get:
1/0.13= 7.7
0.13/0.13= 1
2.23/0.13=17.15
When rounded, the ratio will then be: 8:1:17

KarlaArevalo2F
Posts: 67
Joined: Tue Nov 14, 2017 3:01 am
Been upvoted: 1 time

### Re: Empirical Formula

You would want to start off by dividing with the smallest number, then multiply all of the numbers by the same whole number to get the least whole number possible.