Hey guys, I have about 8-9 questions, so I'm going to cut it down to about 4 per post. I'd appreciate any help that I can get, I have these sample problems, but no answers or workings, and my exam is tomorrow.

1. An AQUEOUS solution contains 3.00 ppm Mg^2+. Determine the [Mg^2+] in mol/L. Assume density of the solution is 1.00 g/mL.


2. A 0.2000 g sample of impure Na3P (contaminated with NaCl) reacts with an excess of water to yield 46.23 mL of PH3(g) in a gas burette at 23.0*C. Atmospheric pressure is 735.0 mmHg and the vapour pressure of water at 23.0*C is 21.2 mmHg. Determine the mass % of pure Na3P in the contaminated sample. PH3(g) is INSOLUBLE in water.


3. A 0.5000 g sample of arsenic (As) is burned in excess oxygen producing 0.7669 g of compound. Determine the empirical formula of the arsenic/oxygen compound.


4. A 0.4362 g sample of a transition metal bromide, MBr3, is dissolved in water and reacted with an excess of AgNO3(aq) producing 0.8424g of AgBr (187.78 g/mol) precipitate. Determine the molar mass and indentity of the transition metal M.


Thanks for any help you guys can offer, and please check out my other post with a couple of more questions.

PLEASE NOTE: This isn't a homework question, I just really need to figure it out before my test, just incase it shows up!