Test – Form 2 First Term

A list of symbols and formulae is shown.

Br₂, Cl^–, CO₂, H₂, K⁺, N₂, O₂, SO₄^2-

Answer the following questions about these symbols and formulae. Each symbol or formula may be used once, more than once or not at all.

State which symbol or formula represents:

1. a molecule containing only five atoms
2. a diatomic molecule of an element in Group VII of the Periodic Table
3. an ion formed when an atom gains one electron
4. an anion
5. a gas that occupies 78% of atmospheric air
6. a Group 1 cation
7. a product of photosynthesis

1. When cobalt(II) oxide, CoO, is heated in air an oxide with the formula Co₃O₄ is formed.

   Balance the equation for this reaction.

   CoO + O₂ → Co₃O₄

2. Hydrogen sulfide burns in air to produce sulfur dioxide and water.

   1. Complete the chemical equation for this reaction.

   H₂S + O₂ → H₂O + SO₂

Chlorine is an element in Group VII of the Periodic Table.

1. Chlorine reacts with phosphorus to produce phosphorus(V) chloride.

   1. Balance the equation for this reaction.

   P + Cl₂ → PCl₅

2. Zinc reacts with phosphorus to form zinc phosphide, Zn₃P₂.

   Complete the equation for this reaction.

   Zn + P → Zn₃P₂

This question is about compounds of sulfur.

1. Hydrogen sulfide has the formula H₂S.

   1. Complete the dot-and-cross diagram to show the electron arrangement in a molecule of hydrogen sulfide. Show outer shell electrons only.

This question is about metals and compounds of metals.

1. A compound of nickel has the molecular formula NiP₄F₁₂.

   Complete Table 4.3 to calculate the relative molecular mass of NiP₄F₁₂.

   atom	number of atoms	relative atomic mass
   fluorine	12	19	12 × 19 = 228
   nickel		59
   phosphorus		31

   relative molecular mass = ………….

Iron ore contains iron(III) oxide, Fe₂O₃. A blast furnace is used to extract iron from Fe₂O₃.

Equations for some of the reactions in the blast furnace are shown.

equation 1: C + O₂ → CO₂

equation 2: CaCO₃ → CaO + CO₂

1. Iron(III) oxide, Fe₂O₃, in iron ore is converted to iron when it reacts with carbon monoxide, CO, in the blast furnace.

   1. Calculate the percentage by mass of iron in iron(III) oxide, Fe₂O₃.

Cobalt is an element in Period 4 of the Periodic Table.

1. 1. Use your copy of the Periodic Table to help you complete the table below.

   particle	number of protons	number of neutrons	number of electrons
   Co
   Co2+

2. ⁶⁰Co is a cobalt isotope.

   1. Explain the term isotope.
3. 1. Explain why two isotopes of the same element have identical chemical properties.

The Kinetic Theory explains the properties of matter in terms of the arrangement and movement of particles.

1. Nitrogen is a gas at room temperature. Nitrogen molecules, N₂, which are spread far apart move in a random manner at high speed.

   1. Draw a diagram showing the arrangement of the valency electrons in a nitrogen molecule. Use × to represent an electron from a nitrogen atom.

Copper is element 29 in the Periodic Table.

1. Copper(II) oxide is formed when copper(II) nitrate, Cu(NO₃)₂, is heated.

   2Cu(NO₃)₂(s) → 2CuO(s) + 4NO₂(g) + O₂(g)

   1. State the meaning of the Roman numeral (II) in the name copper(II) oxide.
2. 1. 0.0200 moles of Cu(NO₃)₂ is heated.
   2. Calculate the mass of 0.0200 moles of Cu(NO₃)₂.
3. 1. Calculate the total volume of gas, in dm³ at r.t.p., produced when 0.0200 moles of Cu(NO₃)₂ is heated.

1. The table below shows the results obtained by reducing the copper(II) oxide.

   1. Complete the table.

   source of copper(II) oxide	mass of copper(II) oxide/g	mass of copper/g	percentage copper/%
   CuCO3	2.37	1.89	79.7
   Cu(OH)2	2.51	1.99
   Cu(NO3)2	2.11	1.68
   Cu and O2	2.29	1.94

1. A compound X contains 82.76% of carbon by mass and 17.24% of hydrogen by mass.

   1. Calculate the empirical formula of compound X.

1. Define the following:

   1. the mole
   2. the Avogadro constant

Ethanoic acid is manufactured by the reaction of methanol with carbon monoxide.

1. Ester Y has the following composition by mass:

   C, 48.65%; H, 8.11%; O, 43.24%. Calculate the empirical formula of ester Y.

2. 1. Ester Z has the empirical formula C₃H₆O and a relative molecular mass of 88. Determine the molecular formula of ester Z.
3. 1. Methylbutanoic acid has the molecular formula C₅H₁₀O₂.
   2. Complete Table 2.2 to calculate the relative molecular mass of C₅H₁₀O₂.

   atom	number of atoms	relative atomic mass
   carbon	5	12	5 × 12 = 60
   hydrogen		1
   oxygen		16

Sulfur is an element in Group VI of the Periodic Table.

1. Sulfur has a relative atomic mass of 32.

   Complete these sentences about the relative atomic mass of sulfur using terms from the list.

   ¹²C, electrons, ¹H, isotopes, neutrons, ¹⁶O, protons, ³²S

   The relative atomic mass of sulfur is the average mass of the sulfur _______.

   This average mass is compared to 1/12^th of the mass of an atom of _______.

1. Which two of the following contain the same number of molecules?

   Show how you arrived at your answer.

   2.0g of methane, CH₄

   8.0g of oxygen, O₂

   2.0g of ozone, O₃

   8.0g of sulfur dioxide, SO₂

1. 4.8g of calcium is added to 3.6g of water. The following reaction occurs.

   Ca + 2H₂O → Ca(OH)₂ + H₂

   1. The number of moles of Ca = _______
   2. The number of moles of H₂O = _______
2. 1. Which reagent is in excess? Explain your choice.

Quantities of chemicals, expressed in moles, can be used to find the formula of a compound, to establish an equation and to determine reacting masses.

1. A compound contains 72% magnesium and 28% nitrogen. What is its empirical formula?