14. Solutions
Vapor Pressure Lowering (Raoult's Law)
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Calculate the vapor pressure in Tore of a solution containing 53.7 grams of Cadmium Nitrate, which has a molecular weight of 236 point 43 grams per mole, and 155 grams of water at 30 degrees Celsius. Here we're told the vapor pressure of pure water at this temperature is 131.8 towards. Alright. So first what we're gonna do is we're gonna calculate the moles of both cadmium nitrate as well as water. So we have 53.7 grams of cadmium nitrate, and we're told for every 1 mole of cadmium nitrate, we have 236.43 grams. So here, when we plug that in, that's gonna give me, moles of 0.22713 moles of cadmium nitrate. And then we're gonna do the same thing with water. We have 1 55 grams of water. For every one mole of water, its mass is 18.016 grams, 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 0.60346 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 1 cadmium ion plus 2 nitrate ions. So that's a total of 3 ions, so I equals 3. So 3 times the moles of cadmium nitrate which is 0.2 2713 moles, plus the moles of water again. Okay. And then that's gonna be multiplied by our 131.8 tours. So when we do that we're gonna get as our final answer, 122 tours for our solution. Here, our answer has 3 sig figs because 53.7 is 3 sig figs and 155 also has 3 sig figs.
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