# Homework Help: Chemistry II: Determining a rate of a Solid

1. May 24, 2006

### Elkay

I'm working on a prelab assignment and couldn't remember exactly what to do in order to solve the following problems. Any help would be greatly appreciated:

a. If 4.0 ml of 0.3M of KI is mixed with 1.0 ml of deionized water, 1.0 mL of buffer solution, 1.0 mL of 0.2 M $$Na_{2}S_{2}O_{3}$$, and 3.0 mL of $$H_{2}O_{2}$$, what is the initial molar concentration of I- (at time=0, before the reaction)?

b. How many moles of $$I_{2}$$ are generated in the rection during the time lapse of the rate measurement? The following equations are given:

$$2 I^- _{(aq)} + H_{2}O_{2} + 2 H_{3}O^+ _{(aq)} \longrightarrow I_{2(aq)} + 4 H_{2}O_{(l)}$$

$$2S_{2}O_{3}^2- _{(aq)} +I_{2}_{(aq)} \longrightarrow 2I^- _{(aq)} + S_{4}O_{6}^2- _{(aq)}$$

Last edited: May 25, 2006
2. May 25, 2006

### siddharth

Do you have any idea/thoughts on the problem? You need to show your work before you get help.

3. May 25, 2006

### Elkay

*sigh*

That's the problem. I don't know where to start or what I need to use to get the problem, so I can't show work.

I'm sorry if I gave the impression that I want someone to solve the problem for me- if I wanted the answer, I could easily just copy the answer from a classmate instead of taking an hour to post my query. I came here hoping someone could give me an idea of what I should do or what I should focus on.

4. May 25, 2006

### siddharth

Sorry for the misunderstanding . It's just that too many posters these days, want only the solutions and don't really want to understand what the problem is about, which annoys me.

Let's take the first question. It asks for the initial concentration of I- before any reaction takes place. First of all, how do you define the molar concentration? Can you think of anyway in which you can apply the definition here?

Last edited: May 25, 2006