If you can answer any of these i would appreciate it! Just posting the ones which i am unsure about, the practice examination papers don't have answer sheets to go with em so decided to nag you guys for some! I have some assumptions on some of the answers. Thanks

**For the reaction 3FeS(s) + 2H3PO4(aq) → Fe3(PO4)2(s) + 3H2S(g), how many moles of**

H3PO4 are required to produce 1 mole of H2S? a.0.67 b. 1.5 c. 2 d. 3

Is the answer 1.5?

**Atoms of Uranium 234U decay by α particle emission. What is the Mass Number of the atom formed as a result? 92**a. 230 b. 231 c. 232 d. 234

I think the answer is a, but i'm unsure

**Atoms of Lead 212Pb decay by β particle emission forming atoms of Bismuth.**

What is the Atomic Number of Bi?a. 83 b. 82 c. 81 d. 80

Think the answer is 83 as it is the atomic number of Bismuth

**If 20 g of a compound is dissolved in water to make 250 mL of a 0.5 mol L-1 solution,**

the Molar Mass of the compound in g mol-1 is:a. 10 b. 40 c. 80 d. 160

Don't know how to work this out, if you do could you please post the formula!

A particular reaction carried out at 60C takes 5 minutes. Approximately how long will it take at 30C ? a. 10 minutes b. 20 minutes c. 40 minutes d. 21/2 minutes

Is the answer 40mins as the every 10 degrees of an decreases doubles the time?

**In which one of the following reactions does an element show the greatest increase in**

oxidation number?a. MnO4- + 8H+ + 5Fe2+ → Mn2+ + 5Fe3+ + 4H2O

b. 2Al + 6H+ → 2Al3+ + 3H2

c. SO2 + 2H2S → 3S + 2H2O

d Cl2 + Sn2+ → 2Cl- + Sn4+

Don't know how to work this out, if you do could you please post how!

**Which one of the following will occur if the temperature of a gas is increased from 30oC**

to 60C? a. The volume will double

b. The volume will increase by a small amount

c. The volume will decrease by a small amount

d. The volume will be halved

Think the answer is A but unsure..

**Which property of water is due to it being a polar molecule?**a. Its boiling point.

b. Its ability as a solvent

c. Its high specific heat

d. All of the above.

I think it's D although i'm unsure

**In which class of compounds has the carbon been most highly oxidized?**a. Carboxylic acids.

b. Aldehydes.

c. Ketones.

d. Alcohols

Think the answer is B, but posted it up just incase it's wrong

Sorry if it's a bit long