C3 - quantitative chemistry

• What methods can be used to measure the mass or volume of reactants or products?

  • Collect products in a gas syringe
  • Use a scale or balance to measure mass
• What should you look for when measuring liquid levels in a container?

  The bottom of the meniscus
• Why is there a degree of uncertainty in measurements?

  Because of the dip in the meniscus
• How is concentration calculated?

  Concentration = amount / volume
• What are the units for concentration, amount, and volume?

  Concentration: moles per decimeter cubed, Amount: moles, Volume: decimeters cubed
• What is the formula for hydrochloric acid?

  HCl
• What is the formula for magnesium?

  Mg
• What products are formed when a metal reacts with an acid?

  Salts and hydrogen gas
• What is the formula for magnesium chloride?

  MgCl$_2$
• How do you balance a chemical equation?

  By ensuring the number of atoms for each element is the same on both sides
• How do you determine the relative formula mass (M.R.)?

  By adding the relative atomic masses of all atoms in the formula
• What is the mass of hydrogen?


  1
• What is the mass of oxygen?

  16
• What is a mole in chemistry?

  A unit for the amount of a substance, equal to $6.022 \times 10^{23}$ entities
• What is the equation for calculating moles?

  Moles = mass / M.R.
• What is the balanced equation for the decomposition of hydrogen peroxide?

  2 H$_2$O$_2$ → 2 H$_2$O + O$_2$
• How do you calculate the mass of oxygen produced from hydrogen peroxide?

  Use the ratio from the balanced equation
• What is the limiting reactant?

  The reactant that is completely consumed in a reaction
• How do you calculate percentage yield?

  Percentage yield = (actual yield / theoretical yield) × 100
• What is atom economy?

  Atom economy = (moles of desired products / moles of reactants) × 100
• What are the steps involved in carrying out a titration?

  1. Use a pipette to add 25 cm³ of alkali to a conical flask.
  2. Add an indicator (e.g., phenolphthalein).
  3. Fill the burette with acid of known concentration.
  4. Record the initial burette reading.
  5. Slowly add acid while swirling until the first permanent color change occurs.
  6. Record the final burette reading.
  7. Repeat until titrations are within 0.05 cm³ of each other.
• How do you calculate the number of moles of acid in a titration?

  By determining the number of hydrogen ions involved in the reaction
• What volume does one mole of gas occupy at standard conditions?

  24 dm³
• What types of calculations are included in the quantitative chemistry topic?

  • Balancing equations
  • Titration calculations
  • Bond enthalpy calculations
  • Mass calculations