quantitative

• What is the definition of relative atomic mass?


  The average mass of all the isotopes of that element
• What is the symbol for relative formula mass?


  Mr
• What is the symbol for relative atomic mass?


  Ar
• what is the formula for percentage mass of an element?


  .

  
• What is the formula that links mass, moles, and Mr?


  • mass = moles x Mr
  • moles= mass / Mr
  • Mr= mass / mass
• what is a chemical change


  a rearrangement of the atoms in the reactants to form the products
• in a chemical reaction is there any change in the overall mass of the substance 


  no
• why is it more difficult to measure the mass of a gas that the mass of a liquid or solid 


  a gas can easily escape to the air
• In a chemical reaction, is there a change in the number of atoms?


  no
• What is the first step in balancing chemical equations?

  Know how to balance chemical equations
• Why is a '2' placed in front of HCl in the equation CaCO3 + 2 HCl → CaCl2 + H2O + CO2?

  To balance the numbers of H's and Cl's on both sides
• What must not be changed when balancing equations?

  You cannot change the formulae
• What does the '2' in front of MgO in the equation 2 Mg + O2 → 2 MgO signify?

  It balances with the 2 O's on the left
• What does the law of conservation of mass state?

  No atoms are lost or made during a chemical reaction
• How can chemical reactions be represented?

  By symbol equations that are balanced in terms of the numbers of atoms
• What is the relative formula mass (Mr) of a compound?

  The sum of the relative atomic masses (Ar) of the atoms in the formula
• How do you calculate the relative formula mass (Mr) of CaCO3?

  Mr = 40 + 12 + (16 x 3) = 100
• What does a balanced chemical equation ensure about the relative formula masses?

  The sum of the relative formula masses of the reactants equals that of the products
• What is produced during the thermal decomposition of metal carbonates?

  Carbon dioxide escapes, leaving the metal oxide as the only solid product
• Why might some reactions appear to involve a change in mass?

  Because a reactant or product is a gas and its mass has not been accounted for
• What happens when a metal reacts with oxygen?

  The mass of the oxide produced is greater than the mass of the metal
• How do you calculate the number of moles of a substance from its mass?

  Using the equation moles = mass/Mr
• What is the unit for measuring chemical amounts?

  The unit is moles (mol)
• What does the mass of one mole of a substance in grams equal?

  It is numerically equal to its relative formula mass
• What is the value of the Avogadro constant?

  1. 02 x 10^23 per mole
• How many particles are in one mole of a substance?

  One mole contains the same number of particles as one mole of any other substance
• How do you calculate the mean and uncertainty of a set of measurements?

  Mean = sum of measurements / number of measurements
• What is the uncertainty of the measurements 20.10, 20.20, 20.00, 20.05, 20.15?

  Uncertainty = ± 0.10 cm³
• How do you calculate the number of moles in 35.0g of CuSO4?

  moles = 35.0 / (63.5 + 32 + 16 x 4) = 0.219 mol
• How do you convert mg to g?

  1000 mg = 1 g
• How do you convert g to kg?

  1000 g = 1 kg
• How do you convert kg to tonnes?

  1000 kg = 1 tonne
• How do you calculate the percentage by mass of an element in a compound?

  percentage by mass = (number of atoms of element x Ar of element) / Mr of compound x 100
• What is the percentage by mass of oxygen in calcium sulfate (CaSO4)?

  47%
• What does Avogadro's Constant represent?

  It represents the number of particles in one mole of a substance
• How do you calculate the number of tin atoms in a 6.00 g sample of tin metal?

  Number of atoms = moles x 6.02 x 10^23
• How do you calculate the mass of 1 atom of sodium?

  Mass of 1 atom = mass of 1 mole of sodium (Ar) / Avogadro’s number
• How do you calculate the number of chloride ions in a 9.50 g sample of magnesium chloride (Mr = 95)?

  Number of ions = moles x 6.02 x 10^23
• What is the limiting reactant?

  The reactant that is completely used up in a reaction
• How does the limiting reactant affect the amount of product formed?

  The number of moles of the limiting reactant determines the number of moles of product formed