## Sapling HW Number 7

Karina Rodriguez 2H
Posts: 50
Joined: Wed Sep 30, 2020 9:34 pm

### Sapling HW Number 7

Hi, I'm having trouble figuring out how to approach question 7. Would I refer to calculating mass percentage composition? The portion of the question regarding water is confusing me.

jasonfarrales3D
Posts: 57
Joined: Wed Sep 30, 2020 9:55 pm

### Re: Sapling HW Number 7

Yes you should refer to calculating mass percentage composition. Basically, the whole mixture consists of calcium chloride and water in which the total mass of it is 691.9g. Moreover, the problem also states that 33.0% of the total mass is calcium chloride, so it's best to assume that the rest of it is composed of water.

.33 * 691.9g = 228.3g calcium chloride
691.9g - 228.3g = 463.6g water

Kaylee Messick 3J
Posts: 57
Joined: Wed Sep 30, 2020 9:54 pm

### Re: Sapling HW Number 7

Hello! The question gives the total mass of the mixture, so you would use the percentage given to find the mass of CaCl2. After subtracting the mass of CaCl2 from the total mass, the remaining mass would be the water since the two components of the mixture are CaCl2 and water. Hope this helps!

Andy Hernandez
Posts: 56
Joined: Wed Sep 30, 2020 9:50 pm

### Re: Sapling HW Number 7

That was very helpful, thanks for the help.

Caelin Brenninkmeijer 1G
Posts: 55
Joined: Wed Sep 30, 2020 9:50 pm

### Re: Sapling HW Number 7

Because the problem gives the total mass of the mixture (718.0g) and the percent of calcium chloride (33.5%), you'd have to find how many grams is 33.5% of 718.0 g is equal to and then subtract that value from the total mass to find the mass of water used.
However, I believe Sapling assigns different values to everyone's problems so you wouldn't be given the same exact numbers.

Posts: 51
Joined: Wed Sep 30, 2020 9:48 pm

### Re: Sapling HW Number 7

Number 7 is quite simple, the only components are CaCl2 and water, it gives the total mass of the compound and the percent of that amount is CaCl2. Just Minus the percent of cacl2 from 100 to get the percent of water, then take the respective percent of what element you want from the total weight of the compound then viola!

905579227
Posts: 44
Joined: Wed Sep 30, 2020 10:01 pm

### Re: Sapling HW Number 7

Hello everyone i was wondering if anyone could help me with molarity because i never really captured it and i feel like im behind on it. Also if anyone whos where to find actual tutors please let me know.

Jacquelyn Challis 2B
Posts: 54
Joined: Wed Sep 30, 2020 9:42 pm

### Re: Sapling HW Number 7

I needed a refresher course on molarity as well, and I found that the video under Audio-Visual Focus-Topics titled "Molarity and Dilution of a Solution" on Lavelle's website to be super helpful.

Hasan Mirza 3F
Posts: 55
Joined: Wed Sep 30, 2020 10:00 pm

### Re: Sapling HW Number 7

905579227 wrote:Hello everyone i was wondering if anyone could help me with molarity because i never really captured it and i feel like im behind on it. Also if anyone whos where to find actual tutors please let me know.

Molarity is the molar concentration of a compound, the formula being M=n/v with the variables standing for Molarity, moles, and volume. Whenever you are given a molarity it refers to the amount of moles that are present within a volume. Molarity is really useful to solve for mass or volume by plugging in whatever you are given to solve for what is missing (like we do in problem 6 of the hw).

Khan academy has some pretty useful stuff if you want to strengthen your understanding or you can check out the stuff on Lavelle's class website.

Savannah Torella 1L
Posts: 52
Joined: Wed Sep 30, 2020 9:40 pm

### Re: Sapling HW Number 7

For number 7, you are trying to find the mass/moles of the solute(n), and you are given the mass percentage of CaCl2. With the mass percentage, you can divide that number by 100 to get the molarity of CaCl2. After finding the volume of the solution (using the periodic table), you can plug M and v into the molarity equation M=n/v. The value n is the mass of CaCl2. To find the mass of H2O used, you first subtract 100% by CaCl2's percent to get H2O's percent. You then repeat the same process that you did for CaCl2.

Jose Miguel Conste 3H
Posts: 57
Joined: Sat Oct 03, 2020 12:15 am

### Re: Sapling HW Number 7

Hi there! For number seven you approach it basically as (if 36% is given by mass) 36 g of CaCl2 /100 g of solution!

Teti Omilana 1G
Posts: 56
Joined: Wed Sep 30, 2020 10:05 pm

### Re: Sapling HW Number 7

For #7, to first get the mass of CaCl2 I just took the percentage of calcium chloride given and multiplied it by the total mass (0.35*660.4). And because you can assume anything left in the solution would be water, you can then take that mass of CaCl2 you got and subtract it from the total mass to get the mass of H20.

Tobie Jessup 2E
Posts: 54
Joined: Wed Sep 30, 2020 10:02 pm

### Re: Sapling HW Number 7

Since the solution is solely CaCl and water, you know that the solution is 36% CaCl by mass (given) and therefore 64% water by mass. The total mass is 855.1 g you can multiply the total mass by .36 to find the mass of CaCl in the solution and .64 to find the mass of water in the solution