Incorrect Questions

• What decreases the percentage uncertainty in the mean titre?

  Use a more dilute solution of sodium hydroxide in the burette.
• Molecules form permanent dipoles when there is a large difference in electronegativity, creating a positive and negative at either end. These then attract the opposite charge of another molecule, creating a dipole-dipole.
• A co-ordinate bond is where only one atom is donating electrons in a covalent bond, or where a bond formed by a shared pair of electrons where both electrons come from one atom.
• State two features of the current atomic model that are not shown in the Rutherford model

  The nucleus contains neutrons and protons, and the different energy levels.
• State an observation of when magnesium reacts with steam

  Bright white light / white powder.
• Give the equation of the reaction between magnesium and steam

  Mg2 (s) + H2O(g) --> MgO (s) + H2 (g)
• Explain how the weak forces between chlorine molecules arise.

  Movement of electrons in one molecule forms a temporary dipole as all the electrons are on one side. This then induces a dipole in a neighbouring molecule. These temporary dipoles attract forming weak van der Waal forces.
• Give an equation for the reaction of chlorine with water

  Cl2 (g) + H2O (l) <-> HClO (aq) + HCl (aq)
• Give an equation for the reaction of chlorine with cold aqueous sodium hydroxide.

  Cl2 + 2NaOH --> NaClO + NaCl + H2O
• State the meaning of the term standard enthalpy of combustion

  Enthalpy change is when one mole of a substance burns completely in oxygen, with all substances in their standard states.
• The enthalpy of combustion determined experimentally is less exothermic than that calculated using enthalpies of formation. Give one reason for this.

  Incomplete combustion
• The student rinses the burette with deionised water before filling with sodium hydroxide solution. What effect does this have on the titre?

  The titre value would increase as the NaOH solution in the burette is more dilute.
• What is the conversion of kelvin to celcius

  -273
• Give the ionic equation between barium and sulfuric acid

  Ba2+ (aq) + SO4 2- (aq) --> BaSO4 (s)