C4 - Dispaclement & Precipitation Reactions and the Transition Elements

Question 1

What is a displacement reaction and why do these work?

Answer 1

It means when a more reactive group 7 element will displace a less reactive group 7 elements from its metal halide. This works because group 7 elements get less reactive as you go down the group.

Question 2

What is the general balanced symbol equation for displacement reactions involving Group 7 elements? Group 7 = X2 and Metal Halide = MY. Give an example using chlorine and potassium iodine.

Answer 2

X2 + 2MY -> Y2 + 2MX

Cl2 + 2KI -> I2 + 2KCL

Question 3

What are the transition elements? General properties?

Answer 3

These elements are placed between Groups 2 and 3 in the periodic table. They are all metals and their properties are typical of metals. For example, in general they are shiny when cut, strong, and malleable.

Question 4

What coloured compounds do the transition elements form? What are they often used as?

Answer 4

• Copper compounds such as copper sulfate solution are
often blue.
• Iron(II) compounds such as iron(II) sulfate solution are
often light green.
• Iron(III) compounds such as iron(III) chloride solution
are often orange-brown.

Often used as catalysts.

Question 5

What is the general word equation for a thermal décomposition reaction involving a metal carbonate?

Answer 5

metal carbonate → metal oxide + carbon dioxide

Question 6

What do precipitation reactions identify ? When do the occur? What exactly is a precipitate?

Answer 6

metal ions in solution. It happens when a mixture of solutions reacts to make an insoluble solid. The insoluble solid is called the precipitate. It makes the mixture cloudy.

Question 7

What is a hydroxide precipitate? What colour precipitate do metal ions form in these reactions?

Answer 7

When a compound of a transition element is dissolved in water, its metal ions separate out. These metal ions react with hydroxide ions to form coloured metal hydroxide precipitates.
Copper (II) - Cu2+ -> blue
Iron (II) - Fe2+ -> grey - green
Iron (III) - Fe3+ -> orange - brown

Question 8

What is the balanced symbol equation for the reaction between copper(II) ions and hydroxide ions, OH–?

Answer 8

Cu2+ + 2OH– → Cu(OH)2