40.00 mL of 1.230-M HNO3 solution and 90.00 mL of 0.104-M HNO3 solution are combined and then diluted with water until the total volume is 250.00 mL. What is th

Question

40.00 mL of 1.230-M HNO3 solution and 90.00 mL of 0.104-M HNO3 solution are combined and then diluted with water until the total volume is 250.00 mL.
What is the molarity of this HNO3 solution? please explain

Answer 1

Hi Dona,

 

For this problem, think about the units of Molarity, moles of solute (HNO₃) per Liter of total solution. So separate these two to start.

 

With the given volumes and a concentrations (Molarity), you are able to calculate moles - Molarity = Moles/Volume, or rearranged, Moles = Molarity x Volume

So what we need to do is find how many total moles of HNO₃ we have from each of the solutions

 

Solution 1 - 0.040L x 1.230M = 0.0492 moles HNO₃

Solution 2 - 0.090L x 0.104M = 0.00936 moles HNO₃

Total Moles HNO₃ = 0.0492 + 0.00936 = 0.05856 moles HNO₃

 

Then, the problem already gives you the total Liters of solution, 250.0mL

 

Therefore, to find the new concentration, we take the total moles of HNO₃ and divide by the total liters of solution

- 0.05856 moles HNO₃/0.250L = 0.234M HNO₃

 

Hope this helps! Let me know if you have questions!