Question

1.how many moles of NaCl are present in 1.0L of a 0.25M solution?
2.show the calculation and describe how to make 1.0L of 0.50M solution when a 5.00M stock solution is available.

Answer 1

1. no. of mole = molarity x volume
2. \[M _{1}V _{1}=M _{2}V _{2}\]

Answer 2

1.
Remember molarity (M) is just a ratio of moles/L

0.25M = 0.25mol/1L

so create an equality

0.25mol/1L = xmol/1L
= 0.25 mol in 1L

solve for x to find the amount of moles

2.show the calculation and describe how to make 1.0L of 0.50M solution when a 5.00M stock solution is available.

Personally I dont like C1V1 = C2V2 formula as it is a waste of time.

So you are just doing a dilution

Just remember (final conc/initial conc)*Final Volume = aliquot to transfer

(0.5M/5.0M)*1L = 0.1L or 100mL

therefore transfer 100mL of to a 1L volumetric flask and fill to the mark.