anyone know how to calculate molarity?

Question

anyone know how to calculate the molarity of each aqueous solution.
(a) 72.0 mL of 0.210 M NaOH diluted to 0.230 L with water?
b) 35.5 mL of 2.0 M HNO3 diluted to 0.220 L with water?

Answer 1

They are simple dilution problems so you can use the dilution formula:

M1*V1 =M2*V2 =>
M2= (V1/V2) * M1
You need to express Volume in the same units so
a) M2= (72/230)*0.210= 0.066 M NaOH
b) M2= (35.5/220)*2.0= 0.32 M HNO3

Answer 2

the number of moles in a sample is the weight of the sample divided by the molecular weight of the substance; it is also the number of molecules in the sample divided by Avogadro's number. Instead of using molecular concentration, it is more convenient to use molar concentration; instead of saying, for example, that the concentration is 12.04 ´ 1023 molecules per litre, it is simpler to say that it is two moles per litre. Concentration in moles per litre (i.e., molarity) is usually designated by the letter M.

Answer 3

Molarity is moles/liter, so
a) 1st find out how many moles there are of NaOH.
.072L*0.210mol/L = .0151 moles of NaOH.
2nd, divide moles NaOH by Liters
.0151moles NaOH/0.230L H2O = .066M NaOH or 6.6x10^(-2) M NaOH

b) .0355L HNO3 * 2.0mol/L = .071mol HNO3
.071mol HNO3/.220L H2O = 0.323M or 3.23x10^(-1)M HNO3

Answer 4

M=moles/L

for dilution problems like this one
M1V1=M2V2

Answer 5

Moles per liter, right?

a) .21 moles divided by .072 liters
b) 2 moles divided by .22 liters
I'll leave the math to you

Answer 6

a. 72 x 0.21 = 0.230x m m =
b. the same way as as