00:02
Hi there.
00:03
In this question, we have a double replacement reaction, or your textbook may call them double displacement.
00:11
The two terms are used interchangeably.
00:13
It just depends on which textbook you're using.
00:16
But a double replacement and a double displacement are the same thing.
00:20
In this type of reaction, the ions exchange places.
00:24
So we are starting with strontium bromide, sr, br2, and it is aquius.
00:33
We're combining that with sodium phosphate, na3, po4, which is also aquas.
00:45
All right, so these are going to exchange ions.
00:48
The positive ion from the first goes with the negative ion from the second, and we need to write the formulas correctly.
00:58
Stronthium has a two positive charge, whereas phosphate has a three negative charge.
01:04
So we need three strontiums and two phosphates so that the total sum of the charges adds to zero.
01:11
Our other product then is going to be the sodium combining with the bromide.
01:18
And it's a positive one negative one, so it's just nabr.
01:22
Okay, looking at the rules for solubility, we see that any ionic compounds composed with a group 1a metal are soluble.
01:32
So the sodium bromide has to be soluble because the sodium's a group 1a metal.
01:38
However, we see that most phosphates, except for group 1a metals and ammonium, phosphates are going to be insoluble.
01:46
So this strontium phosphate is our solid.
01:50
Okay, the next thing we need to do is balance this.
01:53
So we see that there's one strontium on the reactant side, but three on the product side, meaning i need a coefficient of three.
02:00
Three times two gives me six bromides, so coming over here to the product side, i need a six in front of nabr to give me six bromides.
02:09
Now i have six sodiums on the product side and three on the reactant side.
02:14
So i'm 82 in front of na3po4.
02:18
That gives me two phosphates and we have two phosphates on the product side.
02:22
Okay, so we've created the total balanced equation and now we need to write the net ionic equation because that's what the quite answer is asking for is the net ionic equation.
02:36
The net ionic equation shows the ions that combine to produce the precipitate or the solid...