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 in a burette or graduated cylinder?

  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 do you get when a metal reacts with an acid?

  Salts and hydrogen
• 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 equal on both sides
• What is the relative formula mass (M.R.)?

  The sum of the relative atomic masses of all atoms in a 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 happens to the limiting reactant in a chemical reaction?

  It is used up first, stopping the reaction
• How do you calculate percentage yield?

  Percentage yield = (actual yield / theoretical yield) × 100
• What is the purpose of a titration?

  To determine the concentration of an unknown solution
• 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 consistent titers are obtained.
• What volume does one mole of gas occupy at standard conditions?

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

  • Balancing equations
  • Titration calculations
  • Bond enthalpy calculations
  • Mass calculations
• What is the mass of hydrogen peroxide used in the example?

  40.8 grams
• How much oxygen gas is produced from 40.8 grams of hydrogen peroxide?

  19.2 grams
• What is the significance of keeping numbers in the calculator during calculations?

  To avoid rounding errors
• What is the relationship between limiting reactants and the reaction stopping?

  The reaction stops when the limiting reactant is used up
• What is the formula for calculating atom economy?

  Atom economy = (M.R. of desired products / M.R. of reactants) × 100
• What is the role of indicators in titration?

  To signal the endpoint of the titration with a color change
• What color change indicates the endpoint when using phenolphthalein?

  From pink to clear
• What is the importance of repeating titrations?

  To ensure consistent and accurate results
• What is the significance of the term "actual yield" in chemistry?

  The amount of product actually obtained from a reaction
• What does the term "theoretical yield" refer to?

  The maximum amount of product expected from a reaction based on stoichiometry
• What is the purpose of calculating the concentration of an alkali in titration?

  To determine how much alkali is present in the solution
• What is the significance of the relative atomic mass in calculations?

  It is used to calculate the relative formula mass and moles
• How does the concept of moles relate to the number of particles in a substance?

  One mole contains $6.022 \times 10^{23}$ particles
• What is the relationship between mass and moles in a chemical reaction?

  Mass is directly proportional to the number of moles and their relative formula mass
• What is the significance of balancing chemical equations?

  To ensure the law of conservation of mass is upheld
• What is the role of a gas syringe in quantitative chemistry?

  To collect and measure the volume of gas produced in a reaction
• How does the concept of uncertainty affect measurements in chemistry?

  It introduces a range of possible values for a measurement
• What is the importance of using a scale or balance in quantitative chemistry?

  To accurately measure the mass of reactants and products
• What is the significance of the term "excess reactant"?

  It is the reactant that remains after the limiting reactant is used up