## determining x for weak acids and bases

Saachi_Kotia_4E
Posts: 68
Joined: Fri Sep 28, 2018 12:23 am

### determining x for weak acids and bases

when we calculate x for weak acid/base problems, we can disregard x in the denominator when Ka is less than 10^-3, because it doesn't add any significant change to the concentration of the reactants. does this same logic apply to the problems we solved for the chemical equilibrium section?

ThomasLai1D
Posts: 61
Joined: Fri Sep 28, 2018 12:17 am

### Re: determining x for weak acids and bases

I would assume so, because any K < 10^-3 is an indication that such little product is formed to have any significant impact on the final concentrations.

jonathanjchang2E
Posts: 61
Joined: Fri Sep 28, 2018 12:26 am

### Re: determining x for weak acids and bases

Yes, if you need more clarification it is explained on page 441 of the 6th edition textbook in toolbox 11.1.

Ariel Cheng 2I
Posts: 67
Joined: Fri Sep 28, 2018 12:29 am

### Re: determining x for weak acids and bases

I think that you can ignore the x when you are adding it or subtracting it to some constant (e.g. 1.0-x) because the difference that x will make on the number is insignificant when x is that small. It is important to note that x does not equal zero though.

megangeorge-1K
Posts: 59
Joined: Thu Feb 01, 2018 3:01 am

### Re: determining x for weak acids and bases

This is a side note what is a conjugate base/acid?

Shubham Rai 2C
Posts: 64
Joined: Fri Sep 28, 2018 12:27 am

### Re: determining x for weak acids and bases

Conjugate acid is the molecule formed on the product side when a base reacts with water and gains hydrogen. Similarly, a conjugate base is the molecule formed when the acid loses hydrogen during a reaction. Thus, each reaction has a conjugate acid/base pair.

daniella_knight1I
Posts: 57
Joined: Fri Sep 28, 2018 12:18 am

### Re: determining x for weak acids and bases

If the number is so small you can disregard the x because it will have little effect on the number it's subtracting from. A conjugate acid/base is the molecule formed from an acid or a base.

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