The combustion of elements in oxygen
4 marks · NormalThe diagram shows an experiment in which a piece of magnesium ribbon is burned in a bell jar containing air, floating on water as described.
State what you would observe when magnesium burns in the air inside the bell jar.
Write a word equation for the combustion of magnesium in oxygen.
Explain why the level of water rises inside the bell jar after the reaction.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) Bright white light and white powder formed · must show White light or flame, White solid/powder
(b) magnesium + oxygen → magnesium oxide
(c) Oxygen is used up in the reaction and the pressure inside drops, causing water to rise to fill the space. · must show oxygen used up, space filled by water/increased water level
Common mistakes: Saying water rises due to temperature change instead of oxygen removal
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · States bright white light OR white flame, and/or a white solid is formed.
B2 (b) · 1 mark · Correct word equation for magnesium combustion.
M1 (c) · 1 mark · States oxygen is used up/removed during combustion.
M2 (c) · 1 mark · Explains water rises to fill the space left by the used oxygen.
Worked solution
(a) There is a bright white light and a white powder forms on the dish.
(b) magnesium + oxygen → magnesium oxide
(c) The magnesium uses up oxygen as it combusts. The oxygen is removed from the air in the bell jar, so water rises to take its place.