foundations in chemistry Flashcards
(25 cards)
explain what is meant by the term weighted mean mass
the mean mass taking into account the relative abundancies of isotopes
structure and bonding of magnesium
giant lattice
metallic bonding
delocalised electrons
structure and bonding of bromine
simple molecular
London forces between molecules
structure and bonding of magnesium bromide
giant lattice
ionic bonding
between oppositely charged ions
structure and bonding of SiO2
giant covalent lattice
covalent bonds
structure and bonding of CO2
simple molecular
London forces
Why does bromine have a higher bp than chlorine
Bromine has more London forces
Why does a carton of milk expand on freezing
Hydrogen bonds in ice hold H2O molecules further apart than in water
Why is the reaction of ethane with chlorine under UV radiation a poor method for preparing a high yield of chloroethane
Further substitution occurs
Why are the carbon carbon bonds in benzene all the same length
Pi bonds in benzene are delocalised
Why is the rate of hydrolysis of 1-bromobutane faster than that of 1-chlorobutane
The C-Br bond is weaker than the C-Cl bond
The H–O–H bond angle in ice is about 109° but about 105° in gaseous H2O.
Explain why there is this difference.
Ice has hydrogen bonding
Gaseous H2O has 2 bonded pairs and 2 lone pairs
Lone pairs repel more
Explain why a CF4 molecule has polar bonds but does not have an overall dipole.
F is the most electronegative
CF4 is symmetrical
Dipoles cancel
Explain why a small proportion of molecules in water have a relative molecular mass of 20.
Molecules contain deuterium
Predict the name of the shape of, and H–N–H bond angle in NH2–.
Non linear
104.5
Explain why the boiling point of PH3 is lower than the boiling point of NH3.
NH3 has H bonding
Hydrogen bonding is stronger
Explain why the boiling point of PH3 is lower than the boiling point of AsH3
As has more electrons than P
More London forces in AsH3
Which element has the highest first ionisation energy
Helium
SiO2 structure
Giant covalent lattice
a student reacts a sample of ZnCO3 with an excess of dilute HCl in a test tube
describe what the student would see during this reaction
effervescence
and
solid disappears/ dissolves
identify a compound of calcium that could be used to convert a soil from pH 5.8 to 7.5
Ca(OH)2
suggest 2 modifications to the method that would reduce the percentage uncertainty in the mass of the residue
use balance that weighs to more decimal places
use a larger mass
state what is meant by the term ionic bond
electrostatic attraction between positive and negative ions
describe the use of aqueous barium chloride in qualitative analysis
test for sulfate
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