QUANTATIVE CHEM

• what does the law of conservation state?

  no atoms are lost or made during a chemical reaction so the mass of the products equals the mass of the reactants
• what is relative formula mass? (Mᵣ)

  the sum of the relative atomic masses of the atoms in the numbers shown in the formula

  (Mᵣ = mass / moles)
• what is the explanation for a decrease in mass in a reaction + an example?

  - if the vessel isn't enclosed, the gas is able to escape into the atmosphere and decrease the mass

  - in thermal decomposition of metal carbonates, carbon dioxide is produced and escapes
• what is the explanation for an increase in mass in a reaction + an example?


  - if the vessel isn't enclosed, gas in the atmosphere is able to react with the product and increase the mass

  - when a metal reacts with oxygen the mass of the oxide produced is greater than the mass of the metal
• what is the equation for uncertainty?

  uncertainty = range / 2
• what is the value of the avogadro constant?

  6.02 × 10²³
• what is the avogadro constant?


  the number of atoms, molecules or ions in a mole of a given substance
• how do you calculate the number of moles in a substance?

  number of moles = mass (in g) / Mᵣ
• what does the number in front of an element in a balanced chemical reaction represent?

  the number of moles
• what is a limiting reactant?


  the reactant that is completely used up first
• how do you calculate concentration?

  concentration = mass / volume
• how do you convert mol/dm³ to g/dm³?

  using mass = moles × Mᵣ
• why is it not always possible to obtain the calculated amount of a product?

  - the reaction is reversible

  - some of the product may be lost when it is separated from the reaction mixture

  - may have reacted unexpectedly
• how do you calculate percentage yield?

  % yield = (mass of product actually made / maximum theoretical mass of product) × 100
• what is atom economy?

  a measure of the amount of starting materials that end up as useful products
• how do you calculate the percentage atom economy?

  % atom economy = (relative formula mass of desired product / sum of relative formula masses of all reactants) × 100
• what is volume of one mole of any gas at room temperature and pressure?

  24dm³
• what is room temperature and pressure?

  20℃ and 1 atm
• how do you calculate the volume of gas?

  volume of gass = (mass of gas/Mᵣ of gas) × 24