/0's Chem Questions

[/0]

Lol yeah I suck at chem so I probably will be asking a lot of questions

Anyways, whats the difference between a precipitation reaction and a double displacement reaction?

When a gas turns solid, can it be called sublimation, or is that only for solid to gas?


In which of the following reactions is the sulfuric acid NOT acting as a Bronsted-Lowry acid?

A.
B.
C.
D.

Thanks!

[bturville]

The opposite of sublimation (ie. gas to solid) is called deposition (or sometimes desublimation)

A precipitation reaction is when a precipitate forms, this doesn't always occur in double displacements (ie sometimes both products are soluble)

[/0]

thxs bturville!

[/0]

Four containers of gas are set up, with in one, in another, in another, and in the last one.

All containers have a fixed volume of 1.0L, at temperature of 25 degrees celsius and pressure of 1 atm. Which container has the highest density?

[bturville]

Equivalent volumes have equivalent moles at constant temperature & pressure. Use that to try and have a go

[/0]

Equivalent volumes have equivalent moles at constant temperature & pressure. Use that to try and have a go

So they are all the same?

[bturville]

Well no, because they have different atomic masses.

Work out what 1 mole of each of them weighs, to get an idea of which is 'heaviest'. You can just do it roughly in your head by looking at a periodic table and keeping in mind that some are diatomic.

(the answer is Cl2 by the way)

[/0]

Determine the pH of the solution obtained after mixing 90 mL of 0.10M and 10 mL of 0.5M
(assuming that all substances are completely ionised/dissociated)

Here's what I did:

In ,

In ,

So after mixing,




But this is wrong! How come?

[shinny]

You shouldn't be rounding off sig. figs. after every step I think. You should only round off sig figs at your final answer. i.e. 2*0.09*0.1 clearly isn't 0.02.

[/0]

yeah thanks shinjitsuzx, I'll remember that for next time

But how do you actually do the problem?

[Wizard]

n(H₂SO₄) = .090 x .1
n(H⁺) = 2 x .090 x .1
         = .018 mol

n(NaOH) = .010 x .5
n(OH^-) = .010 x .5
          = .005

n(H⁺) - n(OH^-) = .013mol

[H⁺] = .013 / .1
       = 0.13 M

pH = -log [H+]
     = 0.89
 
Numbers may not be right, but thats the general way of working these problems out

[/0]

thanks wizard! I've been confused about that type of question for ages

[/0]

Trick Question:

What is the final volume after adding 50mL of distilled water to 50mL of ethanol?

[shinny]

...50mL? o_o I'm tripping out here.

[/0]

Answer: 98mL, due to hydrogen bonding, dipole-dipole and dispersion forces.

(Page 29 Heinemann Chemistry 2)

We ... uh... we won't need to know this will we? lol
If not, I don't know why they have a diagram showing it :/