00:01
Okay, so this question is asking us to determine the ph of a solution if 25 milliliters of 0 .2 molar hydroiodic acid is added to 0 .028 liters of a 0 .7 molar potassium hydroxide base.
00:21
And so to do this, we just need to first write out our equation.
00:26
And so we are going to have the hi reacting with koh.
00:33
It's a simple acid -base reaction.
00:36
And that's actually going to come over here and form h2o and ki.
00:46
Like i said, acid -base reaction, so water will always be one, and that's our salt is the ki.
00:53
And actually, this equation is already balanced, so we don't have to add any coefficients.
00:58
This is our actual, you know, chemical reaction.
01:01
And so now we can just kind of type in or plug in the numbers that we have.
01:06
So we have 25 milliliters of a 0 .2 molar.
01:08
So let's go ahead and put 0 .2 molar.
01:12
And 25 milliliters is the same as 0 .025 liters.
01:18
We'll come back as to why we did that in a second.
01:21
And we're adding it to a 0 .7 molar koh solution, which is, and we have 0 .028 liters of this.
01:35
So the first thing that we need to do is we need to calculate how many moles of these two solutions there is so that we can properly see it.
01:44
And so we can see which one of these is the limiting reagent, reactant.
01:49
And so to do that, we're going to use our molarity equation, which we need to remember is molarity is equal to moles over liters.
01:57
And so we can solve this or use this equation to figure out the moles.
02:01
So if we want to do this, we can do the molarity of the hydroiodic is 0 .2.
02:08
So we can say 0 .2 molar is equal to the moles of hi over the liters that we used, which is 0 .025.
02:21
And so solving that out, we get that in this reaction, there is 0 .005 moles of hi.
02:34
All right, so now we're going to do the same thing with the koh.
02:39
So we have 0 .7 molar koh, and we know that that is moles over the liters that we used, which in this case is 0 .028 liters, meaning that we had 0 .0196 moles of koh used in this reaction.
03:08
All right, and so we can actually see from this that the smaller one is our moles of the hi, meaning that our hi is the limiting reactant.
03:16
So since this is a one -to -one reaction, we know that every mole that we have of the hi will react with 0 .0196 to form the water and the salt...