Just a chemistry question...see the details.?

Question

How many Kg would be required to make up 200 mL of a 0.0025 M solution of ammonium oxalate monohydrate [ (NH4)2 C2O4 H20]...what is the process and answer? I don't know how to go about this.

Answer 1

calculate the molecular weight of the chemical 142.11 g/mole

calulate the number of moles needed to make the solution by multiplying the desired volume volume by the desired molarity

0.200 liters x 0.0025 Moles/Liter= 0.0005 Moles

0.0005 moles x 142.11 g/mole / 1000g/kg = 0.000071 Kgrams

7.1 x 10-6 Kg

Answer 2

I think you have to disregard the monohydrate portion, because the hydrate will dissappear into the water.

So calculate the molecular mass of the oxalate salt and set up a ratio.

Molarity = # moles / liters of solution
1 mole in 1 liter has a molarity of 1

you want Molarity of 0.0025 = X moles / 0.200 liters.

Solve for moles and then the molecular mass.

For the process, dissolve th ehydrate salt in about 100 mL of water. After fully dissolved, bring the level up to 200 mL

Answer 3

A 0.0025M = 2.5 mM solution has 2.5 micromoles of solute per mL of solution.
So, 200mL of such a solution would contain 500 micromoles of solute. Since its a monohydratated salt, that adds 500 micromoles of water = 500*18 micrograms of water = 9 mg of water, which is aproximately 9 microliters of water. Since this volume is over 4 orders of magnitude smaller than out total volume of 200 mL, no corrections becouse of that extra water are needed.

All that's left is calculating the Mr of your salt. First we count all the atoms:
H: 10
C: 2
N: 2
O: 5
Now we just multiply each number by its corresponding atom's Ar, and add all the results together:
10*1 + 2*12 + 2*14 + 5*16 = 142 g/mole.
So, in order to get 500 micromoles of the salt, we'd have to weight 500*142 micrograms of the salt = 71 mg of the salt.

The process is the usual for making solutions: Weight the 71 mg of the salt, writing down the actual weight used to the tenth's of mg (if you have a proper analytical scale), directly into a 200 mL volumetric flask. Then proceed to fill the flask up to its mark, and shake up.

Answer 4

Steps:

1. Calculate Molecular weight Mw (g / mol)
2. Calculate .0025 M * Mw (g/mol) * .2 Liters /1000g/kg= ? Kg
3. Enjoy!

Answer 5

Molarity = moles/Liters

0.0025M=x/.2L

x= moles

Now calculate formula weight

Then multiply the formula weight by the moles to get the mass in kg