Quantitive Analysis Flashcards
Flame tests method
1) clean nichrome wire loop with concentrated HCl
2) dip the loop into the sample
3) place the loop in the roaring blue flame
4) the colour the flame turns determines the cations present (if a mixture some colours may be masked)
Flame test results
Crimson red - lithium (Li^+)
Yellow - sodium (Na^+)
Lilac - potassium (K^+)
Green - copper II (Cu^2+)
Brick red - calcium (Ca^2+)
Sodium hydroxide test results
White precipitate - Al^3+ or Ca^2+ (Al^3+ dissolves in excess NaOH)
Blue precipitate - Cu^2+
Green precipitate - Fe^2+
Brown precipitate - Fe^3+
No precipitate - NH4^+ (when heated turns damp red litmus paper blue)
Balanced equation of copper chloride + sodium hydroxide
CuCl2 (aq) + 2NaOH (aq) —> Cu(OH)2 (s) + 2NaCl (aq)
Ionic equation of copper chloride + sodium hydroxide
Cu^2+ (aq) + 2OH^- (aq) —> Cu(OH)2 (s)
Testing for carbonates method
1) react the metal carbonate with dilute acid
2) the gas produced will travel along the delivery tube into limewater
3) carbon dioxide turns limewater milky/ cloudy white
Testing for halides method
1) using a pipette, add the chloride/ bromide/ iodide solution into a solution of silver nitrate (AgNO3) and nitric acid (HNO3)
Testing for halides results
White precipitate - chloride
Cream precipitate - bromide
Yellow precipitate - iodide
Testing for sulphates method
1) using a pipette, add the sulphate solution into a solution of barium chloride (BaCl2) and dilute hydrochloric acid (HCl)
2) If sulphates were present, a white precipitate forms
Instrumental analysis advantages
-more accurate
-more sensitive
-quicker
-able to test mulch smaller samples
Instrumental analysis disadvantages
-expensive
-complex (special training needed)
-comparison with other data required
Instrumental analysis examples
-flame emission spectroscopy (to analyse metal ions in a solution)
-flame photometer (to analyse the concentration of metal ions in a dilute solution)
