[Maximum number: 1]

Two groups of students (Group A and Group B) carried out a project* on the chemistry of some group 7 elements (the halogens) and their compounds.

(a)

Group B heated the yellow solid, $\mathrm{CsICl}_{2}$ (s), which turned white and released a brown gas which condensed into a brown liquid.

Group B identified the white solid as CsCl(s). Suggest the identity of the brown liquid.

[ 1 ]

[Maximum number: 1]

Two groups of students (Group A and Group B) carried out a project* on the chemistry of some group 7 elements (the halogens) and their compounds.

(a)

Group B heated the yellow solid, $\mathrm{CsICl}_{2}(\mathrm{~s})$ , which turned white and released a brown gas which condensed into a brown liquid.

Group B identified the white solid as CsCl(s). Suggest the identity of the brown liquid.

[ 1 ]

[Maximum number: 1]

Iron tablets are often prescribed to patients. The iron in the tablets is commonly present as iron(II) sulfate, $\mathrm{FeSO}_{4}$ .
Two students carried out an experiment to determine the percentage by mass of iron in a brand of tablets marketed in Cyprus.
Experimental Procedure:
- The students took five iron tablets and found that the total mass was 1.65 g .
- The five tablets were ground and dissolved in $100 \mathrm{~cm}^{3}$ dilute sulfuric acid, $\mathrm{H}_{2} \mathrm{SO}_{4}(\mathrm{aq})$ . The solution and washings were transferred to a $250 \mathrm{~cm}^{3}$ volumetric flask and made up to the mark with deionized (distilled) water.
- $25.0 \mathrm{~cm}^{3}$ of this $\mathrm{Fe}^{2+}(\mathrm{aq})$ solution was transferred using a pipette into a conical flask. Some dilute sulfuric acid was added.
- A titration was then carried out using a $5.00 \times 10^{-3} \mathrm{moldm}^{-3}$ standard solution of potassium permanganate, $\mathrm{KMnO}_{4}(\mathrm{aq})$ . The end-point of the titration was indicated by a slight pink colour.
The following results were recorded.

(a)

(i)

One titration was abandoned because a brown precipitate, manganese(IV) oxide, formed. State the chemical formula of this compound.

[ 1 ]

[Maximum number: 2]

There are many oxides of silver with the formula $\mathrm{Ag}_{\mathrm{x}} \mathrm{O}_{\mathrm{y}}$ . All of them decompose into their elements when heated strongly.

(a)

(i)

Explain the electrical conductivity of molten $\mathrm{Na}_{2} \mathrm{O}$ and $\mathrm{P}_{4} \mathrm{O}_{10}$ .

[ 2 ]

[Maximum number: 2]

There are many oxides of silver with the formula $\mathrm{Ag}_{x} \mathrm{O}_{y^{.}}$ All of them decompose into their elements when heated strongly.

(a)

(i)

Explain the electrical conductivity of molten $\mathrm{Na}_{2} \mathrm{O}$ and $\mathrm{P}_{4} \mathrm{O}_{10}$ .

[ 2 ]

[Maximum number: 2]

Iron may be extracted from iron (II) sulfide, FeS.

(a)

Iron (II) sulfide, FeS , is ionically bonded.

[ 2 ]

(i)

Describe the bonding in this type of solid.

[ 2 ]

[Maximum number: 2]

Iron may be extracted from iron (II) sulfide, FeS.

(a)

Iron (II) sulfide, FeS, is ionically bonded.

[ 2 ]

(i)

Describe the bonding in this type of solid.

[ 2 ]

[Maximum number: 4]

When heated in air, magnesium ribbon reacts with oxygen to form magnesium oxide.

(a)

State the types of bonding in magnesium, oxygen and magnesium oxide, and how the valence electrons produce these types of bonding.

[ 4 ]

[Maximum number: 2]

A powder has the following percentage composition by mass:
30.0 % sucrose, $\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}$
45.0 % citric acid, $\mathrm{C}_{6} \mathrm{H}_{8} \mathrm{O}_{7}$
25.0 \% sodium hydrogencarbonate, $\mathrm{NaHCO}_{3}$

In the presence of water, the powder effervesces as the citric acid reacts with the sodium hydrogencarbonate:

$3 \mathrm{NaHCO}_{3}(\mathrm{~s})+\mathrm{C}_{6} \mathrm{H}_{8} \mathrm{O}_{7}(\mathrm{aq}) \rightarrow \mathrm{Na}_{3}\left(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7}\right)(\mathrm{aq})+3 \mathrm{CO}_{2}(\mathrm{~g})+3 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})$

(a)

Describe the bonding in solid sodium citrate.

[ 2 ]

[Maximum number: 2]

Phosphorus is an element that is an essential part of the biological molecules involved in both respiration and photosynthesis.

(a)

7.75 g of phosphorus was combusted in a limited supply of oxygen, the mass of the oxide produced was 13.75 g .

[ 2 ]

(i)

This oxide of phosphorus has a melting point of 296.9 K .

Outline, with reference to structure and bonding, the reasons why the melting point of this oxide is low.

[ 2 ]