## X is to small

Andrea_Torres
Posts: 98
Joined: Sun Sep 15, 2019 12:15 am

### X is to small

I read on chemistry community that the x is ignored if the K Is less than 10^-3 but is K always going to be given? If not how will I know when the x should be ignored?

205007651
Posts: 53
Joined: Tue Nov 13, 2018 12:17 am

### Re: X is to small

I believe they should always give you K but I'm not completely sure. Also in the review session today, the K was smaller than 10^-3 but we still couldn't discard the x so I'm slightly confused.

KHowe_1D
Posts: 103
Joined: Thu Jul 25, 2019 12:15 am
Been upvoted: 1 time

### Re: X is to small

If you didn't have K you wouldn't be able to solve for x. So I think we can assume that we either have to solve for K or for x but not both so in a scenario where you solve for x, K should be given.

Posts: 53
Joined: Fri Aug 02, 2019 12:16 am

### Re: X is to small

I believe you can check to see if dropping the x is valid. You do the calculation (with x dropped) and then seeing if the resulting concentration value for x is less than 5 percent of the original concentration of solution (what you started with). If it is, then your approximation is valid.

Sean Tran 2K
Posts: 65
Joined: Sat Aug 17, 2019 12:17 am

### Re: X is to small

X is dropped when it is less than 10^-3 and the percent at the end is less than 5

Ryan Chang 1C
Posts: 105
Joined: Sat Aug 24, 2019 12:17 am

### Re: X is to small

What values do you use to calculate if the percent at the end is less than 5.

Aarushi Solanki 4F
Posts: 107
Joined: Sat Jul 20, 2019 12:17 am

### Re: X is to small

You can disregard x when K is less than 10^(-3) because it will be an extremely small value that won't affect your calculations. However, to ensure that you were correct in disregarding the x value, you must check if x is less than 5% of the original solution's concentration.

Posts: 45
Joined: Sat Aug 17, 2019 12:16 am

### Re: X is to small

When Kc< 10^-3 and x is less than 5% of the initial concentration then it is okay to approximate.

Joanne Lee 1J
Posts: 100
Joined: Thu Jul 25, 2019 12:15 am

### Re: X is to small

K will always be given when solving for x or else there would be no way for us to find x.

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