Created by emilybaitman
over 6 years ago


Isotopes Atoms of the same element with a different number of neutrons
Relative Formula Mass (Mr)ExampleFind the Mr of carbon monoxide COCarbon= 12 Oxygen=1612+16=28Find the Mr of sodium oxide Na2OSodium= 23 Oxygen= 16(23x2)+16=62Molesone moleof that substance. For example, the Mr of carbon monoxide (CO) is 28. This means that one mole of carbon monoxide has a mass of 28 g. You should be able to see that: 14 g of carbon monoxide contains 14 ÷ 28 = 0.5 moles 56 g of carbon monoxide contains 56 ÷ 28 = 2 moles
Empirical FormulaQuestion 3.2g of sulfur reacts with oxygen to produce 6.4g of sulfur oxide.Use the fact that Ar of sulfur is 32 and Ar of oxygen is 16.Answer find the mass of each of the elements first.Oxygen= 6.43.2=3.2Now divide each of the elements mass by its Ar value.Sulfur: 3.2/32=0.1Oxygen: 3.2/16=0.2Fine the ratios of the elements, you can do this by dividing the smallest of the numbers to give you the number of atoms of each element in the compound.Sulfur: 0.1/0.1=1Oxygen: 0.2/0.1=2(if one of these number ever ends in .5 then multiply both numbers by 2)So this tells us that there is one sulfur and two oxygen's so the formula is SO2
New Page