Q. How many moles of chlorine molecules would we find in 71 g of chlorine gas?


A. Chlorine has a relative atomic mass of 35.5 and is routinely diatomic. Therefore the number of moles in 71 g of diatomic chlorine would be exactly 1.


Q. What is the mass in grams of a mole of Iridium?


A. Iridium has a relative atomic mass of 192.22 therefore one mole of iridium would have a mass of 192.22 g


Q. How many moles of nitrogen gas would  we find in 280 g?


A. The relative atomic mass of nitrogen is 14, but nitrogen is routinely diatomic so we have to  double this value to make a relative molecular mass of 28. 280 g of nitrogen would therefore contain 10 moles.


Q. If nitrogen gas was to be monatomic, how many moles would we have in the same amount of gas is in the question previously?


A. If nitrogen was monatomic, we would be looking at a relative atomic mass of 14 and therefore 280÷14 = 20, so this time we will have 20 moles.


If you look back at the 2nd line of the definition we can see that this equally applies to molecules.


Q. What is the mass in grams of 6 moles of sodium chloride?


A. The relative molecular mass of sodium chloride is 58.5 and so 6 moles would contain 6×58.5 = 351 g


Q. How many moles of potassium dichromate would be contained in 100 g of the pure substance?


A. Firstly we need to work out the relative molecular mass of potassium dichromate, the formula for which is K2Cr2O7 .  the relative atomic mass of potassium is 39, for chromium it is 52 and for oxygen it is 16. the relative molecular mass of potassium dichromate is therefore ((2 x 39) + (2 x 52) + (7 x 16) = 216. 100 g of potassium dichromate with therefore contain 100÷216= 0.463 moles to 3 decimal places


Q.How many grams of glucose would be contained in 16.374 moles?


A. Taking the formula of glucose to be C6H12O6 with a relative molecular mass of (6 x 12) + (12 x 1)+ (16 x 6) = 180 the number of grams of glucose in this many moles is 16.374×180 = 2947.32 g


Q. How many moles of water are formed if 2 moles of methane combust completely in oxygen?


A. 



From the balanced equation we can see that one mole of methane requires 2 moles of oxygen molecules (4 moles of oxygen atoms) to combust completely to produce 1 mole of carbon dioxide gas and 1 mole of water. we are told that we have 2 moles of methane and therefore from the equation we can see that 4 moles of water would be produced.


Go To >> Questions <<

Go To >> The Mole <<