Calculating molarity

Question

Calculate the molarity of the solution created when 50.0mL of 0.132M NaOH is mixed with 75.0ml of 0.120M NaOH( assuming that volumes are additive)

Answer 1

Hey Alex.

 

Molarity is measured in moles/liter. So if you know the molarity of your solution, and you know how much solution there is, you know how many moles are present.

 

Your job in this question is to determine how many moles are present in your 50mL solution, and how many moles are present in your 75mL solution. Then sum those up and divide it by your new total volume (50mL + 75mL = 125mL = 0.125L) to determine your new molarity.

 

50mL * 1L / 1000mL * 0.132 mol NaOH/L = 0.0066 mol NaOH

 

75mL * 1L / 1000mL * 0.120 mol NaOH/L = 0.009 mol NaOH

 

Total moles = 0.0066 + 0.009 = 0.0156 mol NaOH

 

Total volume = 0.125L

 

Molarity = 0.0156 mol NaOH / 0.125 L = 0.1248M NaOH

 

Hope this helps.