2. 2. Identify the ions in an ionic compound

Question 1

Identifying cations using flame tests

Answer 1

Apparatus required

Bunsen burner, heatproof mat
Nichrome wire (in holder)
Ionic compounds to test

Sodium chloride, calcium chloride, lithium chloride, potassium chloride, copper(II) sulfate (1 g per salt per group)
Concentrated hydrochloric acid (teacher to control and dispense small quantities or 2 mol/dm3 hydrochloric acid may be used as an alternative)
Safety - Follow safety advice given by teacher

Question 2

Chemical tests to identify ions in ionic compounds - Method

Answer 2

Method
Take a piece of nichrome wire with a loop at one end.
Dip the loop in the concentrated hydrochloric acid and place in the hot blue flame of the Bunsen burner.
Repeat until the flame is no longer coloured, i.e. impurities are removed.
Dip the clean nichrome wire in concentrated hydrochloric acid and the wire onto the solid ionic compound which is sitting in a watch glass.
Hold the loop with the solid ionic compound in the hottest part of the flame and record the characteristic colour.
Repeat for all the solid ionic compounds available, cleaning the wire loop each time.