4.2 Flashcards
4.2 Identifying unknowns (2) STUDENT
• To identify the positive and negative inorganic ions in four solutions, using appropriate apparatus and procedures.
You are given four unknown solutions. Using the chemicals provided you should carry out a series of tests to allow you to identify each solution A–D
Solutions A–D
Treat ALL of these as irritant
Nitric acid, HNO3(aq), of concentration 1.0 mol dm3
DANGER
Causes severe skin burns and eye damage
Silver nitrate, AgNO3(aq), of concentration 0.05 mol dm3
No hazard classification
Can stain the skin
Aqueous barium chloride, BaCl2(aq) 0.2 mol dm3
Harmful if swallowed
Aqueous sodium hydroxide, NaOH(aq) 0.4 mol dm3
WARNING
Causes skin irritation and serious eye irritation
Equipment
- pH indicator paper
- protective gloves
- wash bottle containing distilled (or de-ionised water)
- measuring cylinder (25 cm3)
- beaker (100 cm3)
- glass rod
- conical flask (100 cm3)
- test-tube rack
- four test tubes
- dropping pipettes
- spatula
- bunsen burner
- test-tube holder
Health & Safety
- Wear eye protection throughout.
* You are advised to wear chemical-resistant gloves when handling aqueous nitric acid.
Procedure
The identities of the solutions A–D are listed below in no particular order: • ammonium chloride, NH4Cl (aq) • sodium chloride, NaCl (aq) • sodium hydroxide , Na2CO3(aq) • sodium sulfate, Na2SO4 (aq)
- Plan and carry out a series of tests that would allow you to identify each solution A–D.
- You should carry out the minimum number of tests required. Each test should produce a positive result for at least one of the solutions A–D. You can use any of the chemicals supplied.
- Record the tests you carried out.
- Record all the observations for your tests on solutions A–D.
- Record your conclusions for each test.
- Record the identity of each solution.
Extension Opportunities
1. Write the equations for the reactions you have observed.
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- Write the methods for the experiments you have carried out.
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