Topic 9 Flashcards
solid x contains two ions. the tests:
flame test on solid x - red orange flame
dilute nitric acid is added to an aqueous solution of X, followed by silver nitrate solution - white precipitate forms
use the info to name the cation and anion in solid X
CATION - calcium
ANION - chloride
a test carried out on Y, a few drops of sodium hydroxide solution were added to a solution of Y. a white precipitate formed.
give the reason why this test doesn’t identity the cation in solid Y
more than one cation gives a white precipitate
a test carried out on Y, a few drops of sodium hydroxide solution were added to a solution of Y. a white precipitate formed.
give the reason why this test doesn’t identify the anion in solid Y
sodium hydroxide isnt used to test for anions
instrumental methods are often used for analysis.
give a reason why instrumental analysis may be better than other methods of analysis
gives improved speed, accuracy and sensitivity
iron (II) sulfate solution reacts with sodium hydroxide solution to form a pale green precipitate of iron (II) hydroxide, Fe(OH)2+
write the ionic equation for this reaction
Fe2+ + 2OH- —> Fe(OH)2
all numbers after are small
iron (II) sulfate solution reacts with sodium hydroxide solution to form a pale green precipitate of iron (II) hydroxide, Fe(OH)2+
the green iron (II) hydroxide precipitate gradually turns brown when exposed to air. explain this observation
iron (II) hydroxide oxidised by air. it goes brown due to the formation of iron (III) hydroxide
a sample of potassium carbonate is contaminated with a small amount of sodium carbonate. when a flame test is carried out on the sample, a bright yellow flame is seen.
describe how you could show that potassium and sodium ions are present in this sample
flame photometer and do two sets of emissions
hydrochloric acid reacts with a solution of sodium carbonate :
2HCl(aq) + Na2CO3(aq) —> 2NaCl(aq) + CO2(g) + H2O(l)
write an ionic equation for this reaction
2H+ + CO3 2- —> H2O + CO2
a student test solutions of three ionic substances, K, L, and M. the student carries out the same two tests on each of these three solutions.
TEST 1 - add dilute nitric acid and then silver nitrate solution
TEST 2 - add a few drops of sodium hydroxide solution and warm the mixture
RESULTS:
K) test 1 - white precipitate, test 2 - colourless solution, students conclusion - ammonium chloride
L) test 1 - white precipitate, test 2 - white precipitate, students conclusion - ammonium chloride
M) test 1 - no precipitate test 2 - green precipitate, students conclusion - iron (II) sulfate
none of the conclusions were fully justified, explain which part of the conclusion is justified and what further work can be carried out to fully justify each conclusion.
the chlorine ion is justified as it produces a white precipitate with nitric acid and silver nitrate solution in K and L.
Fe2+ ion is justified because it forms green precipitate with sodium hydroxide solution in M and.
In K ammonium is justified by adding more sodium hydroxide solution and heating. gas evolved turns damp red litmus paper blue.
in L aluminium ion is justified by adding more sodium hydroxide solution until in excess. the precipitate dissolves to give a colourless solution.
in M sulfate ion is justified by adding dilute hydrochloric acid and barium chloride solution, white precipitate forms
a solution, X, is thought to contain chloride, bromide or iodide ios. the solution is tested to see whether it contains one of these ions. in the test a few drops of two different solutions are added to X.
name the two solutions that are added in the test.
solution 1 - nitric acid
solution 2 - silver nitrate
a solution, X, is thought to contain chloride, bromide or iodide ios. the solution is tested to see whether it contains one of these ions. in the test a few drops of two different solutions are added to X.
student carrying out test records : ‘a precipitate forms in the test tube. the precipitate is a cream/yellow colour.
explain why the anion in X cannot be known for certain.
because bromide gas goes cream and iodide goes yellow. other ions may also give these colours.
the metal ions in X could be identified using a flame test, there is a more accurate and sensitive instrumental method that can be used.
give the name of an instrument that can be used to identify the metal ions in X
flame photometer
