Amount of Substance

Relative Atomic Mass- the weighted average mass of an atom of an element, taking into account its naturally occuring isotopes, relative to 1/12th the relative atomic mass of an atom of carbon-12

Relative Molecular Mass- mass of a molecule compared to 1/12th the relative atomic mass of an atom of carbon-12

Avagadro's Constant- the number of atoms in 12g of carbon-12

Empirical Formula- the simplest whole number ratio of atoms of each element in a compound

How many moles are there in 0.53 g of sodium carbonate , Na2CO3?

1.17 g of sodium chloride was dissolved in water to make 500 cm of solution. What is the concentration of the solution on moldm  ?

How many moles of hydrogen molecules are present in a volume of 100 cm  at a temperature of 20.0 C and a pressure of 100 kPa? R = 8.31 JK   mol 

Compound X contains 50.2 g sulfur and 50.0 g oxygen. What is its empirical formula?

How much magnesium chlroide is produced by 0.120 g of magnesium ribbon and excess of hydrochloric acid?

25.00 cm  of a solution of sodium hydroxide, NaOH, of unknown concentration was neutralised by 22.65 cm  of a 0.100 moldm   solution of hydrochloric acid, HCl. What is the concentration of alkali?

0.53 g of compound X containing only carbon, hydrogen, and oxygen, gave 1.32 g of carbon dioxide and 0.54 g of water on complete combustion in oxygen. What is its empirical formula? What is its molecular formula if its relative molecular mass is 58.0?