RICE Tables for Weak Acid/Base Reactions: When to Neglect X?

[oceanflavored]

when you're doing RICE tables for weak acid/base reactions, when do you neglect x? thanks for ANY input

 

[symbolipoint]

What are RICE tables? What does "x" mean?

 

[ssb]

I heard these things called "ICE" tables, but not "RICE" tables... further along I have used these to calculate equilibrium in a system. ICE stands for INITIAL CHANGE EQUILIBRIUM. I never used these things when involving acids/bases.

Here is what Wikipedia sais about RICE tables:

An Indonesian rice table (in Dutch, rijsttafel) consists of rice accompanied by several, often spicy side dishes served buffet-style. Popular side dishes include egg rolls, sambals, satay, fish, fruit, vegetables, pickles, and nuts. It is a Dutch colonial adaptation of the Indonesian makan besar, and popular in both Indonesia and the Netherlands.

The number of side dishes depends mainly on the number of guests; in a restaurant, as many as two dozen side dishes may be served. In many restaurants, the side dishes are brought to the guests' table, covering the table with the many small plates.

 

[oceanflavored]

hmmm.
maybe chemistry has changed a bit since you guys were in high school.
because we calculate weak acids/bases by RICE tables: Reaction, Initial, Change, and Equilibrium; like ssb said.
ok;so never mind.
thanks anyways :)

 

[symbolipoint]

hmmm.
maybe chemistry has changed a bit since you guys were in high school.
because we calculate weak acids/bases by RICE tables: Reaction, Initial, Change, and Equilibrium; like ssb said.
ok;so never mind.
thanks anyways :)

I asked because I never heard of any such acronymic designation. Back several years ago, we used stoichiometry, accounting for concentrations, moles, and some intermediate level Algebra.

 

[gradeaswimr]

haha. you can neglect x if hte 5% rule is valid

 

[gradeaswimr]

for example:

dissociation of HF, Ka = 7.2E-4 HF <-> H+ + F-
I .1 0 0
C -x +x +x
E .1-x x x

Ka = 7.2E-4 = x^2/(.1-x)

- assume 5% rule is valid and x is a very small number in comparison to .1

therefore, 7.2E-4 = x^2/.1

-solve for x, which ends up being about 8.5E-3 which is small in comparison to .1 proving the 5% rule to be valid.

-therefore x can be beglected and the [H+] = x = 8.5E-3

 

[Stevedye56]

We still use ICE tables they haven't meleted yet...haha...