[KGBgringo]

Hi guys, I'm currently doing an access to science course, after 15 years not being in education I occasionally (ok maybe more than occasionally) struggle with the odd question this being one of them...

Calculate the volume of 0.0990 mol/dm^-3 sodium hydroxide solution that is required to neutralise a solution containing 0.148g of ethanoic acid.

CH₃COOH_(aq)+NaOH_(aq) CH₃COONa_(aq)+H₂O_(l)

Any help much appreciated, but please don't give me the answer I need to figure that out myself I just need a gentle prod in the right direction. 

[Arkcon]

OK, you're given the amounts of reactants, but in two different units.  Also, you're given another equation -- the chemical reaction, what are its units?  It has units, they're just not explicitly laid out, but they are understood to be there.

[curiouscat]

Ok, let's try the Socratic method.

Step 1: What's the MW of Ethanoic Acid?

[KGBgringo]

Wow that was quick I went to make a sandwich as wasn't expecting response so quickly. 

So the MW of Ethanoic acid would be 60.

I could then figure out the number of moles by dividing 0.148 by 60 which would be 0.00246, am I right then so now I know the amount of moles in the equilibrium equation.
 

[curiouscat]

I could then figure out the number of moles by dividing 0.148 by 60 which would be 0.00246, am I right then so now I know the amount of moles in the equilibrium equation.

Sounds good so far. 

[KGBgringo]

Right so I'm doing this to 4 sig numbers so calling it 0.0025, ooooooh ok is it now just 0.0025 * 0.148 to get the volume in dm³?

Wait a minute wouldn't I need that 0.148g in cm/dm³

[curiouscat]

Right so I'm doing this to 4 sig numbers so calling it 0.0025, ooooooh ok is it now just 0.0025 * 0.148 to get the volume in dm³?

That multiplication won't make sense. You multiplied moles of Acid by gm of Acid. Why?

Also, didn't see you use the conc. of NaOH yet. That should be relevant, right?

[KGBgringo]

Oh yeah of course, getting confused. 

Would it be the conc * n = vol

so 0.0990 * 0.0025 = 0.0000225 dm³

or 0.0225cm³

[curiouscat]

Oh yeah of course, getting confused. 

Would it be the conc * n = vol

No. Balance units.

[KGBgringo]

oh right is that the times by 24 for cm³ or 24000 for dm³.  Because I got the figure using mass not volume.

Man this is what happens when I understand it in class but due to real life have not got around to doing the homework until a week later, so now it's not fresh in my mind. 

So 0.0000225 * 24,000 = 0.6dm³

Edit: I've got to go out for a bit so if you reply again and I don't I'm not ignoring you, also thank you so much for the help so far is much appreciated. 

[curiouscat]

moles_NaOH = moles_EtAcid

moles = conc. x Vol.

V_NaOH = moles / conc.
= 0.00246 gmol / 0.0990 gmol / dm3
= 0.02485 dm3

Can't guarrentee my math...

[KGBgringo]

Thank you, I was just coming home in the car and had an epiphany of "Nooooo the 24 thing is for gases!!!".  I've still got a day to do this so will crack it properly tomorrow just couldn't get my head round it today for some reason.