Cations Flashcards
What is a cation
Positively charges ion
Nearly all metal ions are cations what’s the exception
Ammonium NH4+
How do flame tests, test for cations
Different metal ions produce different colours when they burn
Describe the procedure for the flame test
Step 1: take platinum (or Nichrome) wire loop
Clean with dilute HCl, rinse in distilled water, heat over Bunsen burner
Step 2: dip the loop into the compound you want to test
Step 3: hold the loop on the blue part of the flame (hottest part)
Step 4: see what colour the flame turns as the compound burns
What colour does lithium ions turn
Crimson
What colour do sodium ions turn
Yellow
What colour do potassium ions turn
Lilac
What colour do calcium ions turn
Orange
What colour do copper ions turn
Green
What is a limitation of the flame test
If there’s more than one compound the colour of the flames will mix
Therefore you can’t tell which metal is present
Describe the metal hydroxide test
React metal ions with sodium hydroxide solution
See what colour the solution turns
What colour precipitate does copper hydroxide form
Blue precipitate
What colour precipitate does calcium hydroxide form
White precipitate
What colour precipitate does iron (II) hydroxide form
Green precipitate
What colour does iron (III) hydroxide form
Brown precipitate
What colour does magnesium hydroxide form
White precipitate
What colour does aluminium hydroxide form
White into colourless
What are the two types of tests for cations
Flame tests
Metal hydroxide test
