Chemical formulae and equationsIB MYP Sciences: Mind map

Exam questions on Chemical formulae and equations

1. A teacher in Lagos burns 0.24 g of magnesium ribbon in an open crucible. The shiny grey metal burns with a bright white flame and leaves a white powder, magnesium oxide. When the powder has cooled, she finds that its mass is 0.40 g.
   Explain why the mass of the white powder is greater than the mass of the magnesium, even though mass is conserved in chemical reactions.2 marks
2. A student in Mumbai places an open flask containing calcium carbonate chips and dilute hydrochloric acid on a balance. The reaction forms calcium chloride solution, water and carbon dioxide gas. Bubbles are seen, and over three minutes the reading on the balance falls from 150.0 g to 148.9 g.
   Explain why the total mass of reactants and products is the same in this reaction, even though the balance reading fell.2 marks
3. A student in Seoul heats 3.18 g of shiny pink-brown copper foil in an open crucible. The copper turns black. When the crucible has cooled, the black solid, copper oxide, has a mass of 3.98 g.
   Write a word equation for the reaction, then a balanced symbol equation with state symbols.3 marks