Relative formula mass, balancing equations, concentrations

• What is relative formula mass represented as?

  Mr
• How is the relative formula mass of a compound calculated?

  By adding the relative atomic masses of all the atoms in the molecular formula.
• What is the formula to calculate the percentage mass of an element in a compound?

  • Percentage mass of an element =

  $\frac{A_r \times \text{number of atoms of that element}}{M_r \text{ of the compound}} \times 100$
• How do you find the mass of iron in a mixture containing 20% iron ions by mass in 50 g?

  By calculating 50 × 20 ÷ 100 = 10 g of iron.
• How can you use moles to calculate masses in reactions?

  By using the balanced equations to determine the number of moles of each substance involved.
• What does the balanced equation Mg + 2HCl → MgCl₂ + H₂ indicate about the moles of reactants and products?

  1 mole of magnesium reacts with 2 moles of hydrochloric acid to form 1 mole of magnesium chloride and 1 mole of hydrogen gas.
• What are the steps to balance equations using reacting masses?

  1. Divide the mass of each substance by its relative formula mass to find moles.
  2. Divide the number of moles by the smallest number of moles.
  3. Multiply to get whole numbers if necessary.
  4. Write the balanced symbol equation.
• What is the balanced symbol equation for the reaction of zinc oxide with carbon?

  2ZnO + C → CO₂ + 2Zn
• What is the relative atomic mass of zinc (Zn)?

  65
• How do you calculate the concentration of a solution in mol/dm³?

  Using the formula: concentration = moles / volume.
• How many moles of NaOH are in 25.0 cm³ of 0.100 mol/dm³ solution?

  0.00250 moles
• What is the balanced equation for the reaction between sodium hydroxide and sulfuric acid?

  2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O
• What is the relative formula mass of sulfuric acid (H₂SO₄)?

  98
• How do you convert concentration from mol/dm³ to g/dm³?

  By using the equation: mass = moles × Mr
• What is the importance of measuring uncertainty in experiments?

  • Helps assess the accuracy of measurements
  • Allows for the evaluation of the reliability of results
  • Provides insight into the range of possible values