Can someone show me how to do these problems? I'm studying for a chemistry exam right now and I am confused about how to solve these questions.
1. A solution with 6.8 mol HCl is mixed with a solution with 15.1 mol of NaOH. How many moles of OH- remain?
2. A solution containing 41.6 mol HCl is mixed with a solution containing 38.7 mol NaOH. The volume is 208 L. What is the final pH?
3. How many moles of H+ are in 143 mL of 0.79 M nitric acid, HNO3?
1.
.................... HCl + NaOH ==> NaCl + H2O
Initial...........6.8 mols + 0............0...........0
add.............................15.1...............................
C................-6.8...........-6.8.....................
E...................0..........15.1 - 6.8 = ?
An easy to way to know how many moles of what is left over.
2. This is done as #1 to solve for how much of which reagent is left over. Then M of that component is M = moles/L. You have moles, L is given in the problem. Then pH = -log (H^+) if acid remains or if NaOH remains calculate
pOH = -log(OH^-) and convert to pH by pH + pOH = pKw = 14. Knowing pOH and pKw you can calculate pH.
3. M = mols/L and rearrange to mols = M x L
You have M given and mL can be convert to L so you can calculate moles.
Post your work if you get stuck or don't understand something.