General Biology

Question

you need to make a solution of NaOH in the lab. You decide to make your solution with 12 g of NaOH in 900 ml of water. You find your solution to have a pH of 10.00, what is the molarity of the solution and concentration of hydroxyl ions in the solution?

Answer 1

12g/40g=0.3 mol NaOH

(0.3 mol NaOH) / (0.900 L solution) =0.33 M NaOH

On the other hand....

If pH=10.00:

pH+pOH=14

pOH=14-pH

pOH=14-10.00

pOH=4.00

[OH-]=10^-pOH

[OH-]=10^-4

Not sure what your prof is talking about. Those are literally contradictory statements.

Also, it's 'hydroxide', not 'hydroxyl'