12 g of magnesium ribbon was heated in a crucible. At the end of the reaction 20 g of magnesium oxide had been produced. What mass of oxygen had reacted with the magnesium?

(a) A piece of magnesium ribbon is ignited and placed in a gas jar of oxygen.The equation for the reaction is 2Mg + O2 → 2MgO (i) Give two observations that would be made in this reaction. (2) 1 ................................................................................................................................................................................................................................................................................ .................................................................................................................................................................................................................................................................................... 2 ................................................................................................................................................................................................................................................................................ ....................................................................................................................................................................................................................................................................................(ii) State why this is an oxidation reaction. (1) .................................................................................................................................................................................................................................................................................... ....................................................................................................................................................................................................................................................................................(b) A second piece of magnesium ribbon is ignited and placed in a gas jar of carbon dioxide.A very exothermic reaction occurs, forming magnesium oxide and carbon.(i) State what is meant by the term exothermic. (1) .................................................................................................................................................................................................................................................................................... ....................................................................................................................................................................................................................................................................................(ii) Give the chemical equation for this reaction. (1) ....................................................................................................................................................................................................................................................................................(iii) A fire starts in a warehouse where magnesium is stored.Suggest why it would not be suitable to use a carbon dioxide fire extinguisher to put out this fire.

(c) A student uses this apparatus to find the mass of magnesium oxide that forms when a known mass of magnesium is heated. magnesium ribbon crucible lid heatThis is his method.• find the mass of the crucible and lid• place some magnesium ribbon in the crucible• find the mass of the crucible, lid and magnesium• heat the crucible with the lid on for a few minutes• find the mass of the crucible, lid and magnesium oxideUsing this method, the mass of magnesium oxide formed is less than expected.Explain two changes that the student should make to his method to obtain a mass of magnesium oxide closer to the expected mass. (4) 1 ................................................................................................................................................................................................................................................................................ .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... 2 ................................................................................................................................................................................................................................................................................ .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... ....................................................................................................................................................................................................................................................................................

The teacher used 1.00 g of magnesium.Use the equation to calculate the maximum mass of magnesium oxide produced.Page 5Give your answer to three significant figures.Relative atomic masses (A r): O = 16; Mg = 24

12 g of magnesium powder was ignited in a container having 20 g of pure oxygen.After the reaction was over, it was found that 12 g of oxygen was left unreacted.Show that it is according to law of constant proportions.2Mg + O2 ⎯→ 2MgO

A magnesium ribbon is burnt in oxygen to give a white compoundX accompanied by emission of light. If the burning ribbon is nowplaced in an atmosphere of nitrogen, it continues to burn andforms a compound Y.(a) Write the chemical formulae of X and Y.(b) Write a balanced chemical equation, when X is dissolved inwater