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Robert Estrada
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Postby Robert Estrada » Thu Dec 07, 2017 9:15 pm

Can someone explain the steps for question 33?
A student added solid Na(2)O to a 200.0-mL volumetric flask, which was then filled with water, resulting in 200.0mL of NaOH solution. 5.00mL of the solution was then transferred to another volumetric flask and diluted to 500.0 mL. The pH of the diluted solution is 13.25. What is the concentration of the hydroxide ion in (a) the diluted solution? (b) the original solution? (c) What mass of Na(2)O was added to the first flask>

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Re: 12.33

Postby Chem_Mod » Sat Dec 09, 2017 10:22 am

Hi, Robert,
Firstly, you need to find pOH as you deal with the base (NaOH). Then, you can find [OH] in your diluted solution. After that, use dilution formula M1V1 = M2V2 to find the [OH] in the starting solution, where V1 is 0.05L (5 ml) and V2 is 0.5L (500 ml). Then, write the reaction: Na2O + H2O = 2NaOH, convert concentration of OH- to moles, convert it into moles of Na2O and find its mass using its molar mass.

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