Module 2 Exam Qs Flashcards
Which sample contains the greatest number of molecules, A=1g of methanol, B=2g of nitrogen dioxide, C=3g of phosphorus, D=4g of iodine 1 mark
B, 2g of nitrogen dioxide NO2
Suggest one modification that the student could make to their method to be confident that all the scandium had reacted. 1 mark
Heat to constant mass
Complete the table to show the number of electrons in the following regions of a europium atom 1s sub shell, 3p orbital, 3rd shell. 3 marks
1s=2, 3p=2, 3rd shell=18
Suggest why the student takes four readings of the mass of the crucible and residue. 1 mark
Make sure all water has been removed
How could the student modify the experiment to be confident that all water of crystallisation has been removed. 1 mark
Heat to constant mass
Which element has atoms with the greatest number of singly occupied orbitals A=C, B=Cl, C=Ca, D=Ga. 1 mark
A, look at number of electrons, write out shells, count number of shells with only one electron in
Which molecule is non-polar, A=SF6, B=H2S, C=PF3, D=NH3. 1 mark
A, draw out diagrams
Which substance contains polar molecules A=C2H4, B=CO2, C=NCl3, D=SF6. 1 mark
C
Describe the bonding in magnesium and silicon. 4 marks
Magnesium has metallic bonding, electrostatic attraction between positive ions and delocalised electrons. Silicon has covalent, between atoms.
State whether the following substances conduct electricity when solid or molten, aluminium, aluminium fluoride, boron tribromide. 5 marks
Aluminium conducts electricity in solid and molten, as it has delocalised electrons. Aluminium fluoride conducts when molten due to free ions and not when solid as ions are fixed in lattice. BBr3 doesn’t conduct electricity when solid or molten as there is no mobile charged particles.
Sbcl3 molecules are polar explain why. 2 marks
Molecule is not symmetrical, dipoles do not cancel out
State and explain 2 anomalous properties of ice caused by hydrogen bonding. 4 marks
Ice is less dense than water, open lattice structure. Ice has relatively high mp/bp than water, hydrogen bonds are stronger.
Explain the boiling points of NH3, -33, F2, -188, Br2, 59. 5 marks
NH3 has hydrogen bonding between molecules. F2 and Br2 have weak intermolecular forces. Forces in Br2 are stronger than F2 because bromine has more electrons than fluorine. The weak intermolecular forces in Br2 are greater than hydrogen bonding in NH3 and hydrogen bonding in NH3 is stronger than intermolecular forces in F2.
