Reacting masses and percentage compositionIB MYP Chemistry: Mind map

Exam questions on Reacting masses and percentage composition

1. A flare manufacturer in South Korea burns magnesium ribbon in oxygen to make a bright white light. The equation for the reaction is 2Mg + O₂ → 2MgO. Relative atomic masses: Mg = 24, O = 16.
   Calculate the percentage by mass of oxygen in magnesium oxide.2 marks
2. A lime works in Morocco heats limestone, calcium carbonate, in a kiln: CaCO₃ → CaO + CO₂. A technician tests a 200 g sample of pure calcium carbonate. Relative atomic masses: Ca = 40, C = 12, O = 16.
   Calculate the mass of carbon dioxide made from the 200 g sample.2 marks
3. A student heats different masses of copper powder strongly in an open crucible so that the copper reacts with oxygen from the air to form black copper(II) oxide: 2Cu + O₂ → 2CuO. She weighs the copper before heating and the copper oxide after cooling. The air supply is always more than enough. Mass of copper and mass of copper oxide formed: 0.64 g and 0.80 g; 1.28 g and 1.60 g; 1.92 g and 2.40 g; 2.56 g and 3.00 g. Relative atomic masses: Cu = 64, O = 16.
   State a testable hypothesis for this investigation, give a scientific reason for it, and state one control variable.3 marks