preparing a solution?

Question

how can we prepare 300 ml of a 2m nacl solution?

can somebody outline all the steps i have a test next week and i don't know how to do these types of question?

Answer 1

number of moles of NaCl = Mass/Mr
also

Number moles NaCl = molarity X vol(cm3)/1000

therefore

Mass/Mr = molarity X vol (cm3)/1000

So, if you rearrange the above:

Mass NaCl you need to dissolve = Mr X molarity X vol(cm3)/1000

In the question molarity is 2M and the volume is 300cm3. I'll let you figure out the Mr of NaCl (just add together the relative atomic masses of Na [23] and Cl[35.5] and arrive at your answer.

Hope it helps.

Answer 2

You will need to determine the number of moles of NaCl to add to 300mL first. Moles = molarity x volume = 2M x 0.300L = 0.6 moles of NaCl.

The molar mass of NaCl = 58.44 g/mol.

Therefore, 0.6 moles of NaCl = 0.6 x 58.44 = 35g NaCl.

To make 300mL of 2M NaCl solution, add 35g of NaCl to enough water to make 300mL of solution.