Calculate the vapor pressure in Tor of a solution containing five 3.7 grams of cadmium nitrate, which has a molecular weight of 236.43 grams per mole in 155 grams of water at 30°C. Here we're told the vapor pressure of pure water at this temperature is 131.8 Taurus. All right. So first what we're going to do is we're going to calculate the moles of both cadmium nitrate as well as water.
So we have 53.7g of cadmium nitrate and we're told for everyone mole of cadmium nitrate we have 236.43g. So here when we plug that in, that's going to give me moles of 0.22713 moles of cadmium nitrate, and then we're going to do the same thing with water. We have 155 grams of water for everyone mole of water. Its mass is 18.016g, so that equals 8.60346 moles of water.
With that we can now figure out the pressure of our solution. So pressure of solution equals the moles of our solvent, so 8.60346 moles of water divided by I is the number of ions your solute will break up into in solution. Cadmium nitrate is ionic, so it breaks up into one cadmium ion +2 nitrate ions. So that's a total of 3 ions. So I = 3. So three times the moles of cadmium nitrate, which is 0.22713 moles plus the moles of water again, OK.
And then that's going to be multiplied by R 131.8 Tors. So when we do that, we're going to get, as our final answer, 122 tours for our solution here, our answer has three sig figs, because 53.7 is 3 sig figs and 155 also has three sig figs.