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Number 33 in the Chapter 12 HW

Posted: Fri Nov 25, 2016 10:35 pm
by Kira Conde 2O
Hi,

I'm having a hard time solving this problem because of the dilutions. It reads:
A student added solid Na2O to a 200 ml flask which was filled with water, resulting in a 200 ml NaOH solution. 5.00 ml was then transferred and diluted to 500 ml. The pH of the diluted solution is 13.25. What is the concentration of the hydroxide ions in A. the diluted solution, b. the original solution, c. what mass of Na2O was added to the first flask?

The dilutions really confuse me, please help!

Kira

Re: Number 33 in the Chapter 12 HW

Posted: Sat Nov 26, 2016 9:45 am
by mikezargari
A) -log[OH-1]=13.25 and solve for [OH-1]
B)once you get [OH-1] use M1V1=M2V2 to find concentration of OH-1 in original solution.
C) (0.2liters/1)(moles of OH-1 which is just molarity value/1 liter)(molar mass of Na2O/1 mol Na2O)