CHemistry help needed!...again

1.Phosphine (PH3) is made from the reaction of hydrogen gas and phosporus. If 120 grams of phosphorus are used how much hydrogen gas i neded for a complete reaction?

2. Consider the reaction of nitrogen gas with chlorine to form nitrogen trichloride. If 37.2 grams of nitrogen gas and 170.4 grams of chlorine are used, what is the yield of nitrogen trichloride?

3.When potassium chlorate is heated, potassium chloride and oxygen gas are formed. The percent yield of the reaction is 83.2%. How much potassium chlorate must be deomposed to produce 198.5 grams of oxygen?

4. A baloon filled with oxygen gas to a volume of 1.75L at 36 degrees celsius. The baloon is then heated to 72 degrees celsius. What is the volume of the heated baloon?

5.A sample of oxyen is collected over water at 22 degrees celsius and 752 mm Hg in a 125 mL flask. How many moles of dry (water vapor excluded) oxygen gas is collected?

 

26.8 grams of copper
Moles = mass/molar mass
= 26.8/63.55 (this is the molar mass of copper)
= 0.42 moles of copper

Copper solid is in a 1:1 ratio to Copper (II) nitrate, so there are 0.42 moles of Copper (II) nitrate also produced.

Therefore find the molar mass of copper (II) nitrate = 187.56g/mol
Moles = mass/molar mass
So mass = moles * molar mass
= 0.42 moles * 187.56g
= 78.78g of copper (II) nitrate is formed.

The other questions are just variants based off this general working. If you're still confused, let me know and I'll do my best to break it down for you.

 

A-level AQA Chemistry?