00:01
There are several ways of expressing concentration, but in general it is expressed as the ratio of the amount of the solute to the amount of the solution.
00:10
In this problem, we're given with an accus solution of ammonia.
00:15
That means ammonia dissolved in water to form the solution, and the concentration expressed in molar is given to be 3 .15 moles per liter.
00:28
Also, its density, d is equal to .975 grams per ml.
00:37
We wish to express these concentrations in percent mass and molality.
00:45
So find letter a, let's say percent by mass of the solution, and for letter b, the molality.
00:55
So let us take note first of the following.
00:58
When you're given with a density that is 0 .975 grams per in this case this means that 1m .l of the solution has a mass of 0 .975 grams so this all pertains to the solution so now to start let us assume we have 1 liter of dissolution so using the molar mass or rather using the molarity will be able to solve for the moles of solute which is nh3 as the molality given times the volume that we assume to be 1 liter so the malality is 3 .15 so malaria is 3 .15 times the volume of 1 liter that means we have 3 .15 moles of nh3 in this solution correspondingly the mass of nh3 we will solve that by multiplying the moles which is 3 .15 by the molar mass of nh3 which is 17 .04 grams per mole so we get molar mass by taking the thumb of the atomic mass of nitrogen and three hydrogen in the compound of nh3 so 3 .15 -17 .04 gives us 53 .6676 of nh3 next we'll solve for the mass of the solution and we will use the density here so first is the given volume or the assumed volume in ml so this is 1 ,000 ml so that's equivalent to 1 liter so again 1000 ml is your 1 liter that we assumed so 1000 ml multiplied by the density of 0 .975 grams per m.
03:01
Giving us 975 grams now this is the mass of the solution note that mass of the solution is equal to mass of dissolute, which is nh3, and mass of the solvent, which is water.
03:22
Why water? because this is an acu solution, so it follows that the solvent is water.
03:29
So, mass of the solution is 975.
03:31
Mass of nh3 is 53 .60, where we have that as 676.
03:37
Therefore we'll be able to get the mass of the solution from the difference of the mass of water rather from the difference of the mass of the solution and the mass of nh3 so 975 minus 53 .676 that gives us 921 .324 grams or in kilograms we'll just divide this value by 1 ,000 since 1 ,000 grams is equal to 1 kilogram...