Chemistry C4

• What is the formula mass represented by?

  Mr
• How is the formula mass (Mr) calculated?

  It is the sum of the Ar of all atoms
• What is Avogadro's constant?

  6.02 x 10²³
• What does one mole of a substance contain?

  6.02 x 10²³ atoms, ions, or molecules
• How many molecules are in one mole of H₂O?

  6.02 x 10²³ molecules
• What is the formula to calculate moles?

  moles = mass/Mr
• What are the steps to use balanced equations for calculations?

  1. Balance the symbol equation.
  2. Calculate moles of known mass using moles = mass/Mr.
  3. Use mole ratio from the balanced equation.
  4. Calculate mass of the unknown substance using mass = moles x Mr.
• What is the difference between limiting and excess reactants?

  • Limiting reactant: runs out first in a reaction.
  • Excess reactant: remains after the reaction.
• What is the first step to identify the limiting reactant?

  Write a balanced symbol equation
• How do you determine which reactant is limiting?

  Calculate moles of each reactant
• What is concentration defined as?

  Amount of solute in a volume of solvent
• What is the unit of concentration?

  g/dm³
• How is concentration calculated?

  concentration = mass/volume
• What happens to concentration with lots of solute in little solution?

  It results in high concentration
• What happens to concentration with little solute in lots of solution?

  It results in low concentration
• How can concentration be measured in mol/dm³?

  Concentration = moles of solute/volume of solution
• What happens to concentration if the amount of solute increases?

  Concentration increases
• What happens to concentration if the volume of water increases?

  Concentration decreases
• How can concentration in mol/dm³ be calculated?

  moles of solute/volume (dm³)
• What is the definition of a mole?

  Mass of a substance containing 6.02 x 10²³ particles
• What is the value for Avogadro's constant?

  6.02 x 10²³ mol^-1
• Which formula calculates moles from mass and Mr?

  moles = mass/Mr
• Which formula calculates mass from moles and Mr?

  mass = moles x Mr
• What is a limiting reactant?

  The reactant completely used up in a reaction
• What is a unit for concentration?

  g/dm³ or mol/dm³
• Which formula calculates concentration from mass and volume?

  concentration (g/dm³) = mass/volume (dm³)
• Which formula calculates volume from concentration and mass?

  volume (dm³) = mass/concentration (g/dm³)
• Which formula calculates mass from concentration and volume?

  mass (g) = concentration (g/dm³) x volume (dm³)
• How can you convert a volume reading in cm³ to dm³?

  Divide by 1000
• What happens to concentration if the amount of solute in a solution is increased?

  Concentration increases
• What happens to concentration if the volume of water in a solution is increased?

  Concentration decreases