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Down the alkaline earths

Science · Chemistry · ages 16-17

Name ______________________ Date ____________

Strontium plus water gives...
- SrO and O2
- No products at room temperature
- Sr(OH)2 and H2
Reactions of Group 2 metals with water down the group get...
- Less vigorous each step
- More vigorous each step
- No pattern down the group
Hydroxides grow less soluble down Group 2.
Circle one: True False
How do the two solubility trends run down Group 2?
- Hydroxides rise; sulfates fall
- Both rise down the group
- Hydroxides fall; sulfates rise
Why does reactivity rise down Group 2?
- The outer electrons move closer to the nucleus
- Outer electrons move farther out behind more shells
- The atoms gain extra neutrons in each shell
Barium oxide plus water gives...
- Ba(OH)2
- Ba + O2 gas
- BaSO4 salt
Why does magnesium hydroxide (milk of magnesia) soothe indigestion?
- It coats the stomach with sulfate
- It neutralises excess acid
- It adds acid to balance the stomach
Why can barium sulfate be swallowed for a scan when barium ions are toxic?
- Stomach acid removes every barium ion
- The salt changes into calcium inside
- It barely dissolves

Answer key

For grown-ups. Fold this page away before handing over the rest.

Sr(OH)2 and H2 · A Group 2 metal reacts with water to form its hydroxide and hydrogen: Sr + 2H2O -> Sr(OH)2 + H2.
More vigorous each step · Ionisation energy falls down the group, so the outer electrons are lost more easily and the water reactions become more vigorous.
False · The hydroxides become more soluble down the group. The sulfates show the falling trend.
Hydroxides rise; sulfates fall · Hydroxides become more soluble, while sulfates become less soluble, down the group.
Outer electrons move farther out behind more shells · Greater distance and shielding weaken the attraction between the nucleus and the outer electrons, so ionisation energy falls.
Ba(OH)2 · A Group 2 oxide reacts with water to form the matching metal hydroxide: BaO + H2O -> Ba(OH)2.
It neutralises excess acid · Milk of magnesia contains magnesium hydroxide. The base reacts with excess stomach acid in a neutralisation reaction.
It barely dissolves · Barium sulfate is very insoluble. Very little enters solution, so most passes through the digestive system rather than supplying many barium ions to the blood.