Water testing Flashcards
What is meant by qualitative analysis?
Investigates the types of substance present in a sample
What is meant by quantitative analysis?
Measuring the amount of substance present in a sample
What does flame test mean?
Flame tests identifies certain metal cations present in a substance
Give examples of flame tests metal cations
Potassium: turns flame lilac
Sodium: turns flame yellow/orange
Copper: blue/green
Calcium: brick red
How do you carry out sodium hydroxide test?
Dissolve substance in water, then add sodium hydroxide solution. An insoluble precipitate should form
Aluminium and calcium both form white precipitate. Describe how you can tell them apart
If aluminium is present then it should redissolve when excess sodium hydroxide solution is added to the precipitate. You can also do a flame test to see if calcium ions are present. The flame should go brick red if it is present
State all five precipitate colours
Aluminium: white- redissolves in excess solution Calcium: white- flame test= brick red Iron 2: green Iron 3: brown Copper: pale blue
Describe how a halide test would be carried out
Add few drops of dilute nitric acid to the sample, then a few drops of silver nitrate solution. A coloured precipitate should form, depending on the halide ions present
What would be formed when carrying out a halide test?
Chloride ions form white precipitate; bromide ions form cream precipitate; iodide ions form yellow precipitates
What is the test for ammonium ions?
Mix sample with dilute sodium hydroxide solution and warm it using a bunsen burner. By now, a distinct smell should be given off due to ammonia. It should turn a damp red litmus paper blue if it is present
What is the word formula for the reaction between silver nitrate solution and sodium chloride solution?
Silver nitrate + Sodium chloride ——-> Silver chloride + Sodium nitrate
What is the balanced and ionic equation for the reaction for silver nitrate and sodium chloride solution?
AgNO3(aq)+NaCl(aq)—>AgCl(s) + NaNO3(aq)
Ag+(aq) + Cl-(aq) ——->AgCl(s)
What does an ionic equation usually show?
Shows two oppositely charged ions reacting to form a solid product
Explain the step for testing carbonate ions
Add dilute hydrochloric acid to a sample containing carbonate ions. You should briefly see bubbles which is the gas carbon dioxide. This can be proven by testing the gas with limewater. It should turn cloudy if carbon dioxide is present
How would you carry out a test to see if a sample of water contains sulfate ions?
Add small volume of water to test tube. Add a few drops of hydrochloric acid, then few drops of barium chloride solution. If white precipitate forms, the water contains sulfate ions
