PAST PAPER QUESTIONS Flashcards
define the term relative atomic mass
the weighted mean mass of an atom compared to 1/12th of a carbon-12 atom
solid sulfur exists as a lattice of S8 molecules
each S8 molecule is a ring of eight atoms, how many atoms of sulfur are there in 0.0120 mol of S8 molecules?
0.0120 x 8 = 0.0960
describe how london forces arise?
at any instant there may be an uneven distribution of electrons which will cause a temporary dipole
this will induce a temporary dipole on neighbouring molecules and they will be weakly attracted to eachother
suggest why there are no other intermolecular forces in solid sulfur
because there’s only one type of element so there’s no difference in electronegativity
sulfur hexafluoride, SF6, exists as a non-polar covalent molecules with an octahedral shape
explain why a molecule of SF6 has an octahedral shape
because it has 6 bonding pairs and no lone pairs
so electron pairs repel equally
explain what is meant by the term electronegativity and suggest why SF6 molecules are non-polar
electronegativity refers to an atoms ability to attract electrons in a covalent bond
SF6 molecules are non-polar because they’re symmetrical so the dipoles cancel out
what is the name of the term used to describe the repeating patterns in the periodic table?
periodicity
why does magnesium have a greater second ionisation energy than strontium?
magnesium has a smaller radius
magnesium has less shielding
so there’s more nuclear attraction between the nucleus and outermost electrons and more energy is needed to remove the outer electron
write an equation to show how HClO can form in drinking water
Cl2 + H2O -> HClO + HCl
suggest a reason why scientists may be worried by the presence of chlorine compounds in water
chlorine compounds are toxic
what is a dative covalent bond?
a shared pair of electrons where both electrons are donated by one atom
what is used as the standard measurement of relative isotopic mass?
carbon - 12
chemists are able to predict the shape of a simple covalent molecule from the number of electron pairs surrounding the central atom
explain how this enables chemists to predict the shape
electron pairs repel so they arrange themselves for minimal repulsion
the shape is determined by the number of bond pairs and the number of lone pairs of electrons
define, in words, the term first ionisation energy
the energy required to remove an electron from each atom in 1 mole of gaseous atoms
what would the student observe when making a solution of strontium chloride by adding excess dilute hydrochloric acid to strontium carbonate
they would see bubbles and the solid dissolve
