Q3

• How many metres are in 35mm?

  0.035 m
• Substance X is a compound containing 632mg of manganese and 368mg of oxygen. Substance X is shown below. Manganese has a relative atomic mass of 55 and oxygen has a relative atomic mass of 16. What is the value of y in the formula below?

  MnOy

  manganese : oxygen Mass = 0.632g : 0.368g Ar = 55 : 16 Moles of manganese = 0.632 / 55 = 0.0115 Moles of oxygen = 0.368 / 16 = 0.023 Ratio of moles = 0.0115 : 0.023 = 1 : 2 Empirical formula = MnO2
• True or false? A graph of the product formed in a reaction plotted against the amount of limiting reactant used will always be a straight line through the origin.

  True

  The limiting reagent directly influences the amount of product formed. If the limiting reagent is doubled, then the amount of product will double.
• True or false? You can follow the progress of a reaction that produces a gas using a sensitive mass balance, because the mass of the reaction vessel increases as the gas is produced.

  False

  The mass of the reaction vessel will decrease as the gas produced leaves the reaction vessel.
• The formula for ammonia is NH3. Which is greater: the number of molecules in one mole of ammonia, or the number of atoms in one mole of ammonia?

  atoms in one mole