Homework Help: Science (Chemistry)

Posted by Dylan on Sunday, November 6, 2011 at 10:18am.

I'm not sure how to do a couple of problems on my chemistry worksheet. Can you please help me?

You dissolve 0.00902 g of naOH in enough water to make 1000 mL. What is the Ph of this soultion.

What is the molarity, pH, and pOH of 5.00 of naOH in 750.0 mL of soultion. I know how to do the pH and the pOH usaully but how do I do it with the g?

Last question:
You take 2 mL of 18.0 M H2SO4 and add it to 998 mL of wate4r. What is the pH and pOH?
Can you please show me how to do these... I'm lost. Thanks

Science (Chemistry) - bobpursley, Sunday, November 6, 2011 at 11:52am
convert the grams to moles.

Molarity=mass/molmass / volumesolution

= .00902/40*1 = you do it.

Now the dissociation equation:
NaOH>>Na+ + OH-
completely dissociated, so the moles of NaOH become the concentration of Na+, and OH-

pOH= -log(molarity above)
pH= 14-pOH

same thing on the sulfuric acid, except the molarity determination.
moles of H2SO4=.002*18=.036
Molarity= .036/1.0=/036
or another way:
you are diluting it 1000/2=500 times, or new molarity= 18/500=.036M

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