general chemistry chapter 5

Question

What NaCl concentration results when 249ml of a 0.740m NaCl solution is mixed with 427 ml of a 0.380m NaCl solution?

Answer 1

I assume by 0.740m NaCl, you mean 0.740 M NaCl, for molarity.

It's easiest to not treat this like a dilution.

If you want molarity you need moles and liters.

Molarity = moles / total L

Moles in 249mL of a 0.740M NaCl

1000mL=1L

249mL=0.249L

0.740M=moles÷0.249L

=0.184 moles NaCl

moles in 427 mL 0.380 M NaCl:

427mL=0.427L

0.380M=moles÷0.427L

=0.162 moles

total moles = 0.162+0.184=0.346 moles

total volume=427mL+249mL=676mL=0.676L

molarity=moles÷L

molarity=0.346÷0.676

=0.512 M NaCl