C3 - quantitative chemistry

• What is the relative formula mass of MgCl₂?

  95
• How do you calculate the relative formula mass of a compound?

  Add the atomic masses of its elements
• What is the atomic mass of magnesium (Mg)?

  24
• What is the atomic mass of chlorine (Cl)?

  35.5
• How do you calculate the percentage mass of an element in a compound?

  Use the formula: (A × number of atoms) / Mr × 100
• What is the atomic mass of sodium (Na)?

  23
• What is the relative formula mass of sodium carbonate (Na₂CO₃)?

  106
• How do you find the percentage mass of sodium in sodium carbonate?

  Calculate: (2 × 23 × 100) / 106
• What is the percentage mass of sodium in sodium carbonate?

  43.4%
• What does a mixture containing 20% iron ions by mass mean?

  It contains 20 g of iron in 100 g
• How much iron is in a 50 g mixture with 20% iron ions?

  10 g of iron
• How do you calculate the percentage mass of iron in iron chloride (FeCl₃)?

  Use the formula: (A × number of atoms) / Mr × 100
• What is the atomic mass of iron (Fe)?

  56
• What is the relative formula mass of iron chloride (FeCl₃)?

  162.5
• How much iron chloride is needed to provide 10 g of iron?

  23 g of iron chloride
• What is the formula to find the number of moles in a given mass?

  Number of moles = mass ÷ Ar
• How many moles are in 66 g of carbon dioxide (CO₂)?

  1.5 moles
• What happens to mass in a chemical reaction?

  Mass is always conserved
• Why does mass seem to change in a reaction?

  Usually due to a gas being involved
• How can you use moles to calculate masses in reactions?

  Use balanced equations to find ratios
• What is the balanced equation for magnesium and hydrochloric acid reaction?

  Mg + 2HCl → MgCl₂ + H₂
• What are the steps to balance equations using reacting masses?

  1. Calculate moles of each substance.
  2. Divide by the smallest number of moles.
  3. Multiply to get whole numbers if needed.
  4. Write the balanced equation.
• What is the mass of zinc oxide (ZnO) that reacts with carbon?

  8.1 g of zinc oxide
• What is the atomic mass of zinc (Zn)?

  65
• How do you calculate the number of moles of substances in a reaction?

  Divide mass by relative formula mass
• What is the balanced equation for the reaction of zinc oxide and carbon?

  2ZnO + C → CO₂ + 2Zn
• What is the definition of limiting reactants?

  Reactants that are completely used up
• How does the amount of product depend on the limiting reactant?

  The product amount is determined by the limiting reactant
• How do you calculate the mass of aluminium oxide formed from aluminium?

  Use the balanced equation and moles
• What is the atomic mass of potassium (K)?

  39
• What is the atomic mass of bromine (Br)?

  80
• What is the atomic mass of chlorine (Cl)?

  35.5
• What is concentration a measure of?

  How crowded things are in a solution
• How is concentration measured?

  In g/dm³
• What is the concentration of a solution with 10 g of NaCl in 0.2 dm³?

  50 g/dm³
• What is the concentration of a solution with 15 g of salt in 100 cm³?

  150 g/dm³
• How do you find the mass of solute in a solution at a known concentration?

  Rearrange the concentration formula
• What is the pH scale used for?

  • Measuring acidity or alkalinity
  • Ranges from 0 to 14
  • Lower values indicate acidity
  • Higher values indicate alkalinity
• What is neutralization in chemistry?

  • Reaction between an acid and a base
  • Produces salt and water
  • Balances pH levels
• What is conserved in a chemical reaction?

  Total mass of all substances