Group 2

• State the trend in first ionisation energies as you descend group 2:

  Decreases
• Why do the first ionisation energies of the atoms decrease down group 2?

  Number of full energy levels increases so outer electrons are more shielded from nucleus so less attraction.
• State the trend in melting point down group 2:

  Decreases
• Why does the melting point decrease down group 2?

  Size of positive ion increases but charge of ion stays the same. The EFA between positive ions and delocalised electrons decreases. Hardness decreases too.
• What happens to the solubility of the sulphates down group 2?

  Solubility of sulphates decreases.
• Which sulphate is soluble in water?

  Magnesium sulphate (MgSO4)
• Which sulphate is sparingly soluble in water?

  Calcium sulphate (CaSO4)
• What is formed when barium ions are added to sulphate ions?

  A white precipitate
• Which sulphates are insoluble in water?

  Strontium sulphate (SrSO4) and Barium sulphate (BaSO4)
• What happens to the solubility of the hydroxides down group 2?

  Solubility of hydroxides increase.
• Which hydroxide is insoluble in water?

  Magnesium hydroxide- Mg(OH)2
• Which hydroxide is sparingly soluble in water?

  Calcium hydroxide- Ca(OH)2
• Which hydroxides are soluble in water?

  Strontium hydroxide- Sr(OH)2 and Barium hydroxide- Ba(OH)2
• What is formed when dilute NaOH is added to MgCl2?

  A white precipitate
• What is formed when dilute NaOH is added to CaCl2?

  A faint white precipitate
• What happens to the reactivity of group 2 metals with water down the group?

  Reactivity with water increases.
• Which element does not react with water or steam?

  Beryllium
• Which element does not react readily with water but reacts with steam?

  Magnesium
• What is observed when magnesium reacts with water?

  A white precipitate
• What is observed when magnesium reacts with steam?

  A bright white light and a white solid is formed.
• Which products are formed when magnesium reacts with water?

  Magnesium hydroxide and hydrogen gas.
• Which products are formed when magnesium reacts with steam?

  Magnesium oxide and hydrogen gas.
• Which element reacts steadily with cold water?

  Calcium
• What happens to the solution when calcium reacts with cold water?

  Turns cloudy as the hydroxide is not very soluble.
• What is observed when calcium reacts with water?

  A slight white precipitate
• Which elements react vigorously with cold water?

  Strontium and Barium
• What is observed when strontium or barium react with cold water?

  Fizzing
• What is formed when strontium or barium react with cold water?

  Colourless solution as strontium and barium hydroxide are both soluble in water.
• Equation for magnesium reacting with water:

  $Mg(s)+$$2H2O(l)\ \rightarrow\ Mg\left(OH\right)2(s)+$$H2(g)$
• Equation for magnesium reacting with steam:

  $Mg(s)+$$2H2O(g)\ \rightarrow\ MgO(s)+$$H2(g)$
• Equation for calcium reacting with cold water:

  $Ca(s)+$$2H2O(l)\ \rightarrow\ Ca\left(OH\right)2(s)+$$H2(g)$
• What is the pH of the solution when magnesium reacts with water?

  pH 9
• What is the pH of the solution when calcium reacts with water?

  pH 10
• What is the pH of the solution when strontium or barium react with water?

  pH 14
• Why is the pH of the solution with calcium higher than with magnesium?

  Ca(OH)2 is more soluble in water than Mg(OH)2 so gets a higher concentration of OH- ions.
• Why is the pH of the solution with magnesium 9?

  Mg(OH)2 will partially dissociate into ions as it is very insoluble in water.
• Why do solutions containing strontium or barium have a pH of 14?

  Sr(OH)2 and Ba(OH)2 are both strong bases. They fully dissociate into ions in water. High concentration of OH- ions so high alkaline pH.
• What is the use of magnesium hydroxide?

  Taken to relieve indigestion
• What is the use of calcium hydroxide?

  Neutralise acidic soil.
• What is the use of barium sulphate?

  Can be eaten as part of a “barium meal” to absorb x-rays.