Sapling Assignment 1 Question 6

[IsabelMurillo3K]

Hey guys!
I was wondering if anyone could explain how to properly convert the units on problem number 6 of the sapling homework.
The problem is: If 2.92 g of CuNO3 is dissolved in water to make a 0.260 M solution, what is the volume of the solution in milliliters?
So far I know that I have to use the equation M=N/V with M being molarity, N being moles of solute, and V being volume, and I've switched the equation to V=N/M because the problem is asking for volume. I'm just confused with how to cancel out the grams on top with the units of molarity on the bottom. If anyone could help me out I would really appreciate it, and thank you in advance!

[Sydney Lam_2I]

Hi!

You'll need to convert the grams of CuNO3 to moles of CuNO3 using the molar mass of the compound. From there you can use the equation M=n/V to solve for the volume! Remember that the volume that is produced is in L and you'll need to convert them to mL.
Hope this helps!

[claire ikemiya_2I]

The grams are cancelled out because you have to start by converting the 2.92 g of CuNO3 into moles. Then you take that value and plug it into the N of your equation, V = N/M. Hope that helps!

[Praneetha Kakarla 3A]

Hey, you just need to convert the mass to moles. The molar mass of CuNO3 is 125.56 g/mol, so the amount of CuNO3 in moles is 2.92/125.56=0.0233 mol. So now you can plug that into the V=n/M formula (molarity is just mol/L) to give V=0.0233mol/0.260mol/L=0.0894 L. The question asks for the volume in mL, so 0.0894 L = 89.4 mL.

[Ansh Patel 2I]

Start off by converting 2.92g CuNO3 into moles using the molar mass, which is about 125.56 g*mol^-1. After you have calculated this, divide the moles of CuNO3 by the molarity of the solution (n/M). Knowing that the units for molarity is moles per liter, just multiply the volume you calculated in the last step by 1000 to get your answer in mL.

[Stephen Min 1I]

You would first convert 2.92 grams CuNO3 to moles and get .0232 moles CuNO3. Then, you can divide the moles by the molarity of .260 in order to get volume. Because M represents mol/L the moles in the numerator would cancel out with the moles in the denominator leaving you with a volume of .0892 L or 89.2 mL

.0232 mol / .260 mol/L = .0892 L or 89.2 mL

[Heather Szeszulski 1I]

Hello! I just solved this problem, how to cancel the grams out is you need to convert it into mols using the molar mass! once you do that grams will cancel out (that will give you your n) from there plug into the equation and mult by 1000 to get final answer in mL. hope that helped :)

[EmilyC_3D]

To solve the problem, you would need to convert your units for CuNO3 from grams to moles! You can find the molar mass using the periodic table and then divide grams/molar mass. Then you should be able to use this value and the molarity to find the volume by using M=n/V as you mentioned in your post.

[Rob Tsai 2F]

This one gave me a bit of trouble too! I feel like this question is classic when it comes to questions about molarity. They give you the grams of whatever compound you are dissolving into a solution and the molarity/volume, but they don't give you the last component you need that would let you plug and chug into the formula M=(n/V), which, in this case, are the moles of the compound. It adds an extra component where you have to derive the moles yourself by dividing the mass by the molar mass.

In this case, you would find the molar mass of CuNO3 by adding up the individual molar masses of Cu, N, and O3. Once you do this, dimensional analysis tells you that to get moles out of the units that are given, you have to divide the grams by the g/mol. Once you do this, you can solve for the volume! Hope this helps!

[Alen Huang 2G]

It can be really helpful on questions like these if you just write out the units. For example, (2.92 grams)(?) = ? moles, you know that you need to convert grams to moles which means u need mole per gram, which is just the molar mass.

() being multiplication.

[Kathy_Li_1H]

Hi! So you have to first convert the grams of CuNO3 to moles, which can be done by dividing the grams of CuNO3 by the molar mass of CuNO3. The units for this operation would be grams divided by grams/moles; therefore, you would be left with moles as the unit. Afterward, with the moles of CuNO3 that you just found, you have to input this value into the equation M=n/V (or V=n/M, either are perfectly fine!). hope this helps :)

[Lily Mohtashami]

You need to make sure you convert the grams to moles so that when you dive your units will be ml=M/(M/ml) and the moles will cancel.

[Namratha Gujje]

You have to convert the grams value into moles. The problem says you have 2.92 grams of CuNO3 so you find the molar mass of CuNO3 and divide those two values to find moles:

2.92/125.55 = 0.023 moles of CuNO3. From here you can easily find the volume by plugging our known values

0.023 moles/0.260 M = 0.885 liters

[Annette Fishman]

You have to convert the grams into moles using the molar mass. You have 2.92 grams of CuNO3 so you find the molar mass of CuNO3 and divide those two values to find moles:

2.92/125.55 = 0.023 moles of CuNO3.
grams/(grams/mol) = mole

From here you can easily find the volume by plugging in known values

0.023 moles/0.260 M = 0.885 liters

And the problem asks for ml, so convert the units!

[Melanie Lin 3E]

Hi Isabel!

The first thing you'll need to do is find the moles of CuNO3 by dividing the 2.92 g by the molar mass of CuNO3. With the M=N/V equation, you can put 0.260 M for M and the moles of CuNO3 for N. With two of the variables substituted with values, you can find the volume in liters. From there you'd convert the liters into milliliters (1000 mL = 1 L). Hope this was helpful!

[Michael Sun Dis 3G]

You would first need to convert from grams to moles using the molar mass of CuNO3. Then you can just plug in the molarity and moles into the equation M = n / V, and solve for volume. Your answer would be in liters, and so you would have to convert it to milliliters by multiplying it by 1000.

[Talia Dini - 3I]

Hi! First, you would convert 2.92 g of CuNO3 to moles of CuNO3 by dividing 2.92 g by 187.56 g/mol (molar mass of CuNO3). Afterward, you would divide the moles of CuNO3 by the molarity of the solution. Lastly, you would convert the volume of the solution to ml by multiplying by 10^3.