Similarities & Trends in the Properties of the Group 2 Metals, Magnesium to Barium, & Their Compounds (CIE AS Chemistry)

When a firework is lit a fuel, and an oxidising agent reacts.

In such a firework, magnesium is the fuel, and barium nitrate is the oxidising agent. 

Which solid products are produced when the firework is lit?

1	BaO
2	MgO
3	Mg(NO3)2

Group II nitrates undergo thermal decomposition according to the following equation.

X(NO₃)₂  XO + 2NO₂ + O₂

Which Group II nitrate requires the highest temperature to bring about its thermal decomposition?

The diagram shows some applications of compounds of Group II elements.

Which numbered links are correct?

	Magnesium oxide	Calcium carbonate
A B C D	4 and 5 only 4 and 6 only 5 only 6 only	1, 2 and 3 1, 2 and 3 1 and 3 only 1 and 3 only

Which mass of solid residue will be obtained from the thermal decomposition of 5.10 g of anhydrous calcium nitrate?

Use of the periodic table is relevant to this question.

Thermal decomposition of magnesium nitrate, Mg(NO₃)₂, produces a white solid and a mixture of gases. One of the gases released is oxygen. 

32.3 g of anhydrous magnesium nitrate is heated until no further reaction takes place. 

Use of the periodic table is relevant to this question.

What is the mass of oxygen produced?

In agriculture, lime can be added to damp soil to change the pH. This can be followed by the addition of a nitrogenous fertiliser ammonium sulfate. This will result in a chemical reaction in the soil. 

Which substances were formed in this reaction?

1	Sulfuric acid
2	Calcium sulfate
3	Ammonia

As you go down Group II, what are the trends in the properties in the table below?

	Decomposition temperature of the carbonate	First ionisation energy
A B C D	Decreases Decreases Increases Increases	Decreases Increases Increases Decreases

When quicklime, water and sand are mixed, it makes lime mortar. Lime mortar hardens over time. Aqueous hydrochloric acid reacts with fresh and old lime mortar, but only the old lime mortar effervesces during the reaction. 

Which equation describes the change from fresh to old lime mortar?

A compound was thermally decomposed to a constant mass; this gave off a colourless gas that reacted with limewater. The limewater went cloudy. The solid that was left was allowed to cool, and aqueous hydrochloric acid added, a vigorous effervescence was seen.

Use of the periodic table is relevant to this question.

What was the mineral compound?

Thermal decomposition of compound S releases carbon dioxide gas and forms a white solid, T. S and T are not soluble in water. Compound T is used as a refractory kiln lining.

What is compound S?

Solids Q, R, S and T are compounds of two different Group II metals. A few of the uses of these are detailed below. 

Compound Q is used as a refractory lining material in kilns. 

Compound R is used as a building material. It can also be heated in a kiln to form compound S. When S is hydrated; it forms compound T, which is used agriculturally to treat soils. 

Which statements about these compounds are correct?

1	More acid is neutralised by 1.0 g of R than by 1.0 g of Q
2	The Mr of R is greater than the Mr of S by 44.0
3	The metallic element in S reacts with cold water more rapidly than the metallic element in Q

An anhydrous nitrate of a Group II metal was thermally decomposed. 6.00 g was used, and 3.06 g of gas was produced. 

Use of the periodic table is relevant to this question.

What is the nitrate compound?

A mixture of 2 Group II elements, Y, were thermally decomposed.

This reaction produced a white solid and only two gaseous products. One of the gaseous products relights a glowing splint. 

What could be the components of mixture Y?

Use of the periodic table is relevant to this question.

Thermal decomposition of anhydrous magnesium nitrate, Mg(NO₃)₂, gives a white solid and a mixture of two gases R and S.

S is oxygen.

What is the ratio ?

When equal volumes of saturated solutions of barium hydroxide and calcium hydroxide are mixed, a white precipitate, Y, forms. The mixture is filtered, and carbon dioxide is bubbled through the filtrate, producing a second white precipitate, Z. 

What are Y and Z?

	Y	Z
A B C D	Ba(OH)2 Ba(OH)2 Ca(OH)2 Ca(OH)2	Ca(OH)2 CaCO3 BaCO3 Ba(OH)2

A colourless solution was formed when metal Y was reacted with water. This solution then gave a white precipitate when mixed with aqueous sulfuric acid.

What is metal Y?

A student performs several experiments on element Y, an alkaline earth metal to determine its identity and the following observations are made:

1	When added to water, Y-hydroxide dissolves in water.
2	When added to water, Y-sulfate produces a white precipitate.
3	In order to thermally decompose Y-nitrate, more heat is required than to thermally decompose strontium nitrate.
4	When burned in oxygen Y will readily become YO.

What is the identity of element Y?

Group II metal carbonates can be used as fire retardants as they thermally decompose producing CO₂. The CO₂ removes the oxygen from the fire. Three minerals each having a mixture of two Group II metal carbonates could be used as fire retardants.

               Barytocite     BaCa(CO₃)₂ 

               Dolomite        CaMg(CO₃)₂

               Huntite                 Mg₃Ca(CO₃)₄

What is the order of effectiveness as a fire retardant, from best to worst?

	Best                                Worst
A B C D	Dolomite Dolomite Huntite  Huntite	Barytocite Huntite  Dolomite Barytocite	Huntite Barytocite Barytocite Dolomite

Thermal decomposition of the nitrates of beryllium, calcium, magnesium, and strontium produce the same products. When 4.00 g of one of these anhydrous nitrates is decomposed, 2.64 g of gas is produced. 

Use of the periodic table is relevant to this question.

What is the nitrate?

In which row of the table are all statements comparing magnesium and barium correct?

	First ionisation energy of magnesium	First ionisation energy of barium	Reaction of magnesium with oxygen	Reaction of barium with oxygen
A B C D	lower lower higher  higher	higher higher lower lower	faster slower faster  slower	slower faster slower faster