Reacting masses and percentage compositionIB MYP Chemistry: Flashcards

What these 13 flashcards ask

What are the four steps for finding a reacting mass?
What does the mole ratio come from?
How do you convert mass to moles?
How do you convert moles to mass?
What is the formula for percentage by mass of an element in a compound?
What is the percentage of oxygen in MgO?
What is the percentage of iron in Fe₂O₃?
What should the percentages of all the elements in a compound add up to?
What is a limiting reactant?
What is a reactant in excess?
How do you find which reactant is limiting?
What mass of CaO is made from 100 g of CaCO₃?
Why is the mass of magnesium oxide greater than the mass of magnesium burned?

Exam questions on Reacting masses and percentage composition

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
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
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

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).