Vapor Pressure Lowering Example 1

Jules Bruno
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calculate the vapor pressure in tour of a solution containing 53. g of cadmium nitrate, which has a molecular weight of 2 36.43 g per mole in 155 g of water at 30 degrees Celsius. Here we're told the vapor pressure of pure water at this temperature is 1 31.8 tours. Alright. So first, what we're gonna do is we're gonna calculate the moles of both kaboom nitrate as well as water. So we have 53.7 g of cadmium nitrate and we're told for every one mole of cadmium nitrate, We have to 36.43 gramps. So here, when we plug that in, that's going to give me a moles of .22713 moles of cadmium nitrate. And then we're gonna do the same thing with water. We have 155g of water For every one mole of water. Its mass is 18.016 gramps. So that equals 8.60346 moles of water. With that, we cannot 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 salute will break up into a solution. Kaboom nitrate is Ionic, so it breaks up into one cadmium ion plus two nitrate ions. So that's a total of three ions. So I equals three. So three times the moles of cadmium nitrate, which is .22713 moles plus the moles of water again. Okay. And that's gonna be multiplied by R 1318 tours. So when we do that, we're gonna get as our final answer tours for our solution here. Our answer has three sig figs because 53.7 is 36 figs and 55 also has three sig figs.