chem hel please?

Question

calculate the number of moles of 5 mL of 0.004M AgNO3 and number of moles of CrO4^2- in 5mL of 0.0024M K2CrO4.

can someone please help me answer this question?
thank you

Answer 1

Use the equation:-
moles(n) = [Conc] x volume /1000
n(AgNO3) = 0.004 x 5 /1000 = 2.0 x 10^-5 moles

Similarly,
n(CrO4^2-) = 0.0024 x 5 / 1000 = 1.2 x 10^-5 moles

NB
Conc is quoted as 'M' - moles per litre (dm^3), therefore because volume is in mL (cm^3) the calculation must be divided by 1000 because there are 1000 mL in one litre (dm^3) in order to reduce the units to moles.
NNB
The potassium chromate dissolves in solution
K2CrO4 -- > 2 K^2+ + CrO4^2-
the molar ratio of K2CrO4 : CrO4^2- is 1:1. So the moles of CrO4^2- is also 0.0024. The potassium component can be ignored.

Answer 2

5 mL 0.004M AgNO3
0.004M=x moles/ 0.005L
x=0.00002 moles AgNO3

5mL 0.0024 M K2CrO4
0.0024M=x moles/ 0.005L
x=0.000012moles K2CrO4
0.000012moles K2CrO4 (1mol CrO4/1mol KrCrO4) = 0.000012 moles Cr04

I think that's right.

Answer 3

You know that molarity is moles/L, right?

So, you have a volume of a solution. Convert that to liters and multiply it by the molarity. Both of the ions that you're interest in are present in 1 ion/formula unit.

Answer 4

ok Number of Moles = Volume(in liters) x Molarity
a) = 0.005L x 0.004M = 2 x 10 ^ -5
b) = 0.005L x 0.0024M=1.2x10^-5
good luck
rock

Answer 5

Mole day was on tuesday

Answer 6

I am not going to help you with your homework (plus I have no idea what the answer is), if you really need help go in early and ask your teacher, get a tutor, or google it.

Answer 7

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