Group 7 Flashcards
What happens when the halogens are oxidised with metals?
Reduced to negative halide ions
What happens when halogens are oxidised with nonmetals?
Noble gas configuration of often achieved through covalent bonding
What are the physical properties of the halogens?
Nonmetallic elements that exist as diatomic molecules
Very reactive and strong oxidising agents
Less reactive as you go down the group
Nonpolar so dissolves in hydrocarbon solvents
How does splitting it into aliquots in a titration affect the accuracy of results?
Decreases accuracy
Smaller titration volume so larger percentage error
What is the general equation for a reaction between the halogens and sodium hydroxide in a cold dilute alkali?
X2 + 2OH- (aq) –> X-(aq) + XO-(aq) + H2O
What is the equation for the decomposition of halate I ions?
3XO- –> 2X-(aq) + XO3-(aq)
What does the products of the disproportionation reaction of halogens depend on?
The temperature
All examples of halogens when alkalis are disproportionation reactions
What can be observed when the hydrogen halides react with ammonia gas?
White smoke so it can be used to test for a hydrogen halide
What is the general equation for the reaction between ammonia gas and hydrogen halides?
NH3 (g) + HX(g) –> NH4X(s)
Which is a stronger oxidising agent? Chlorine or iodine?
Chlorine
What does concentrated sulphuric acid reacts with the halide to form?
NaCl(s) + H2SO4(l) –> NaHSO4(s) +HCl(g)
What does sulphuric acid act as when it reacts with a halide?
Oxidising agent
What is produced when sodium bromide and sulphuric acid react?
Br2 H2O SO2
What is produced when sodium iodide and sulphuric acid react?
H2S H2O I2
What is the test for chloride ions?
Silver nitrate
White precipitate
Soluble in dilute ammonite
Darkens in sunlight
What is the test for bromide ions?
Silver nitrate Cream precipitate Insoluble in dilute ammonia Soluble in concentrated ammonia Darkens in sunlight
What is the test for iodide ions?
Silver nitrate
Yellow precipitate
Insoluble in concentrated ammonia
Is the ionic equation for the reaction between silver nitrate and chloride?
Ag+ + Cl- –> AgCl(s)
If C4H9I is used instead of C4H9Br, the rate of formation of C4H9NH2 increases. Why?
The C-I bond is much weaker than the C-Br bond
Why might there be a difference between the students mean titre and the accurate value other than due to limitations in the equipment?
Judgement of colour at endpoint
Adding starch too early
How do you determine how many significant figures to calculate an answer to?
Least accurate measurement in the experiment/calculation
