# Basic chemistry questions

1. Nov 4, 2006

### konartist

Hey guys I need some help on some chemistry questions (any help will help)

1. Is it more correct to write H+ (aq) or H3O+(aq)? Explain.
Now, as far as I know, these both mean the same thing, but we'd prefer to write H+ to help understand pH level right? I'm not too sure.

2. In words, what is the mass of 1 mole of any molecule?
The mass of one molecule is avagadros number right?

3. How many milliliters of 1.0 M HCL have to be added to neutralize 50 mL of 0.25 M NaOH?

I have not a clue where to start, if someone could tell me a formula, or get me started on this, I may be able to finish it.

Much thanks!

2. Nov 4, 2006

### geoffjb

Typically, it comes down to context. Technically, $H^{+}$ becomes $H_{3}O^{+}$ in water.

No, Avagadro's number is the number of molecules/atoms/things in one mole of that molecule/atom/thing. The mass of one mole is the molar mass (try to convince yourself why).

To start, write out the formula. Figure out the molar ratio (1:1, 2:1, 1:2, etc.), which is determined from the coefficients of the balanced formula. Then, determine how many moles you have of NaOH, and use the mole ratio to determine how many moles of HCl are needed to neutralize this. Finally, convert that amount (i.e. moles) into a volume. Watch your units throughout.