Covalent bonding

Crude oil is a mixture of hydrocarbons.

The majority of hydrocarbons in crude oil belong to one homologous series.

Give the name of this series.

When hydrocarbons undergo combustion, water is produced.

Draw a dot and cross diagram of a molecule of water.

One compound in crude oil contains 0.96 g of carbon atoms combined with 0.32 g of hydrogen atoms.

Calculate the empirical formula of this compound.

(relative atomic masses: C = 12, H = 1.0)

*(d) Crude oil is separated into useful products called fractions using fractional distillation.

Figure 9 shows a fractional distillation column and the fractions kerosene and fuel oil.

Kerosene and fuel oil have different uses depending on their properties.

Describe the properties and uses of kerosene and fuel oil. Include in your answer

• the difference in boiling point

• the difference in viscosity

• the difference in ease of ignition

• their uses and how fuel oil can be converted into kerosene.

Crude oil is a mixture of hydrocarbons.

The majority of hydrocarbons in crude oil belong to one homologous series.

Give the name of this series.

When hydrocarbons undergo combustion, water is produced.

Draw a dot and cross diagram of a molecule of water.

One compound in crude oil contains 0.96 g of carbon atoms combined with 0.32 g of hydrogen atoms.

Calculate the empirical formula of this compound.

(relative atomic masses: C = 12, H = 1.0)

empirical formula of this compound =_........

This question is about the properties of different substances.

Silicon tetrachloride is a simple molecular covalent compound.

A molecule of silicon tetrachloride is composed of a silicon atom and four chlorine atoms.

• a silicon atom has 4 outer electrons

• a chlorine atom has 7 outer electrons

Draw a dot and cross diagram of a molecule of silicon tetrachloride, SiCl₄.

Show outer electrons only.

Explain why simple molecular covalent compounds such as silicon tetrachloride have low melting and boiling points.

Part of the structure of rubidium bromide is shown in Figure 4.

Which row shows the most likely melting point and boiling point of rubidium bromide?

*(c) Diamond and graphite are two forms of carbon.

Figure 5 shows how the carbon atoms are arranged in a part of the structure of each of these forms of carbon.

• diamond is one of the hardest known substances on Earth and is used in cutting tools.

• graphite is soft and flaky.

• diamond is a poor electrical conductor, but graphite is a good electrical conductor.

Explain, in terms of structure and bonding, these properties of diamond and graphite.

Magnesium is a metal.

State one physical property of magnesium.

Which element is in the same group of the periodic table as magnesium? Use the periodic table to help you answer this question.

Magnesium atoms have 12 electrons.

Complete the electronic configuration of a magnesium atom.

The electronic configuration of a chlorine atom is 2.8.7

Explain how the electronic configuration of chlorine is linked to its period in the periodic table.

1.20 g of magnesium reacts completely with 3.55 g of chlorine to form magnesium chloride.

Calculate the empirical formula of the magnesium chloride.

(relative atomic masses: Mg = 24.0, C l = 35.5)

You must show your working.

empirical formula =_........

Sodium reacts with chlorine to form sodium chloride, which contains ionic bonds.

Hydrogen reacts with chlorine to form hydrogen chloride, which contains covalent bonds.

Figure 6 shows dot and cross diagrams of these compounds.

Describe the differences between an ionic bond and a covalent bond.

Figure 1 shows the structure of a molecule of each of four compounds, A, B, C and D.

The formula of a molecule of compound A is H₂O.

Give the formula of a molecule of compound D.

The names of two of the compounds in Figure 1 are shown below.

Draw one straight line from each name to the structure of a molecule of that compound.

Figure 2 shows information about the number of electrons in the outer shell of each of the different atoms in a molecule of compound C.

Use the information in Figure 2 to complete the dot and cross diagram for a molecule of compound C.

The atomic number of phosphorus, P, is 15.

One atom of phosphorus has a relative atomic mass of 31.

Give the number of protons, neutrons and electrons in this atom of phosphorus.

number of protons =_........

number of neutrons =_........

number of electrons =_........

Chlorine is an element in group 7 of the periodic table.

What name is given to group 7 of the periodic table?

Chlorine reacts with sodium to form sodium chloride.

Write the word equation for this reaction.

Chlorine, Cl₂, is made of simple molecules.

Describe what is meant by the term molecule.

Sodium, like all metals, conducts electricity.

Explain how sodium conducts electricity.

Sodium chloride contains sodium ions, Na⁺, and chloride ions, Cl^–.

Use this information to state the formula of sodium chloride.

Sodium chloride is made of a giant structure of ions.

Which diagram shows the arrangement of particles in sodium chloride?

Sodium chloride solution conducts electricity.

State what can be put into the circuit in Figure 8 to show that a current is flowing.

Figure 9 shows a flow diagram of how hydrochloric acid can be made.

Balance the equation for the reaction between hydrogen and chlorine to form hydrogen chloride.

H₂ + Cl_{2 ........} HCl

State how hydrogen chloride can be converted into hydrochloric acid.

Figure 5 shows the percentage of three gases, X, Y and Z, in the Earth’s early atmosphere.

What is the name of gas Z ?

It is thought that small quantities of hydrogen sulfide, H₂S, were also in the Earth’s early atmosphere.

Draw the dot and cross diagram for a molecule of hydrogen sulfide.

Show outer electrons only.

Acid rain is caused by some pollutant gases present in the atmosphere.

Explain how impurities in fossil fuels can result in acid rain.

A student investigates the effect of acid rain on cress plants.

The student uses this method.

step 1 grow 20 cress plants in each of two dishes, A and B

step 2 water the cress plants in dish A with 10 cm³ of dilute hydrochloric acid with a pH of 2

step 3water the cress plants in dish B with 10 cm³ of pure water with a pH of 7

step 4 repeat steps 2 and 3 every day for one week

step 5 count how many plants are still alive after one week.

State what piece of equipment the student could use to measure the pH of each liquid.

Explain one improvement that the student could make to the method to make the results more valid.

Figure 5 shows a sample of hydrogen peroxide solution decomposing to form water and oxygen gas.

Write the word equation for hydrogen peroxide solution decomposing.

In this reaction hydrogen peroxide is a solution, water is a liquid and oxygen is a gas.

Draw one straight line from each substance to its correct state symbol.

Describe the test to show the gas produced is oxygen.

Figure 6 shows the electron arrangement for an atom of hydrogen and an atom of oxygen.

Complete the dot and cross diagram in Figure 7 for a molecule of water, H₂O.

Draw outer shell electrons only.

Liver contains the enzyme catalase.

A piece of liver was added to another sample of hydrogen peroxide solution.

Figure 8 shows the results.

Figure 9 shows a graph of the volume of oxygen produced from the hydrogen peroxide with and without liver.

Figure 9

Complete the missing label on the axis of the graph.

Describe what the graph shows about the difference in decomposition of hydrogen peroxide with and without liver.

Describe how the apparatus in Figure 8 could be modified to find the volume of gas produced when the liver is added to the hydrogen peroxide.

When solid sodium chloride is mixed with water, sodium chloride solution forms.

What name is given to the process of mixing a solid with water to form a solution?

Sodium reacts with hydrochloric acid to form sodium chloride and hydrogen.

Write the word equation for this reaction.

The hazard symbol shown in Figure 1 is used on containers of sodium.

What is the meaning of this hazard symbol?

Hydrogen has one electron in its electron shell. Figure 2 shows the incomplete dot and cross diagram of a hydrogen molecule.

Complete Figure 2 to show the electrons in the covalent bond between the two atoms of hydrogen.

The pH of a sodium chloride solution was measured.

State what could be used to measure the pH of a solution.

Sodium chloride solution is neutral.

Give the pH of this solution.

Figure 1 shows the apparatus that can be used to electrolyse sodium sulfate solution using inert electrodes.

Hydrogen is produced at the negative electrode during electrolysis.

Describe the test to show the gas is hydrogen.

What is the name of gas X that forms at the positive electrode?

State what is meant by the term electrolysis.

The sodium sulfate solution was made by dissolving 28.4 g of sodium sulfate in water to make 250 cm³ of solution.

Calculate the concentration of this solution in g dm⁻³.

Give your answer to three significant figures.

concentration =_........ g dm

The word equation for the reaction between copper carbonate and dilute sulfuric acid is

copper sulfuric copper carbon

Complete the balanced equation for this reaction.

CuCO₃+_{........ ........} + CO₂+ H₂O

Calculate the relative formula mass of copper carbonate, CuCO₃. (relative atomic masses: C = 12.0, O = 16.0, Cu = 63.5)

relative formula mass of CuCO₃ =_........

What is the chemical test to show that a gas is carbon dioxide?

Figure 2 shows a conical flask containing dilute sulfuric acid. Copper carbonate is added to the acid in the flask. The copper carbonate is added one spatula measure at a time until the reaction has finished.

State two observations that would show the reaction has finished.

The electronic configuration of carbon is 2.4 The electronic configuration of oxygen is 2.6

Draw a dot and cross diagram for a molecule of carbon dioxide.

Show outer electrons only.

Chlorine, bromine and iodine are elements in group 7 of the periodic table.

Chlorine is toxic.

State one safety precaution that should be taken when using chlorine in the laboratory.

Chlorine reacts with hydrogen to form hydrogen chloride.

Write the word equation for this reaction.

Hydrogen chloride dissolves in water to form an acidic solution.

State what is seen when blue litmus paper is placed into this solution.

A chlorine atom has seven electrons in its outer shell. A hydrogen atom has one electron in its outer shell.

Complete the dot and cross diagram of a molecule of hydrogen chloride. Show outer shell electrons only.

Name the type of bonding in a molecule of hydrogen chloride.

If chlorine solution is added to sodium bromide solution a reaction occurs.

chlorine + sodium bromide sodium chloride + bromine

Give a reason why this reaction occurs.

Figure 5 shows apparatus used to find out if a solution conducts electricity.

Glucose solution and sodium chloride solution are tested. Glucose is a typical simple molecular covalent compound. Sodium chloride is an ionic compound.

State what would happen to the lamp when glucose solution is tested.

State what would happen to the lamp when sodium chloride solution is tested.

Figure 6 shows how the conductivity of one solution changes as its concentration increases.

Figure 6

Describe how the conductivity of this solution changes as its concentration increases from 0 to 500 g dm^–3.

In Figure 5, the letters A, E, G, J, X and Z show the positions of six elements in the periodic table.

These letters are not the symbols of the atoms of these elements.

Using the letters A, E, G, J, X and Z

give the letters of the two elements that are non-metals

give the letters of two elements in period 2

give the letter of an element that normally forms an ion with a charge of +1.

Element E has an atomic number of 5. In a sample of E there are two isotopes. One isotope has a mass number of 10 and the other isotope has a mass number of 11.

Explain, in terms of subatomic particles, what is meant by the term isotopes.

All atoms of element E in this sample contain

Element X has an atomic number of 18.

State the electronic configuration of an atom of element X.

In an experiment, 3.5 g of element A reacted with 4.0 g of element G to form a compound.

Calculate the empirical formula of this compound. (relative atomic masses: A = 7, G = 16)

You must show your working.

empirical formula of this compound =_........

An oxygen atom has six electrons in its outer shell.

A hydrogen atom has one electron in its outer shell.

Complete the dot and cross diagram of a molecule of water, H₂O.

Show outer shell electrons only.

Covalent substances can be simple molecular covalent or giant covalent.

Ammonia is a simple molecular, covalent substance.

Which is the most likely set of properties for ammonia?

Ammonia, NH₃, is made by reacting nitrogen with hydrogen.

Write the balanced equation for this reaction.

Oxygen, O₂, is also a simple molecular, covalent substance.

Draw a dot and cross diagram for the molecule of oxygen.

*(c) Figure 5 shows the arrangement of carbon atoms in diamond, graphene and a fullerene (C₆₀).

Consider these three substances.

Explain, in terms of their structures and bonding, their relative melting points, strengths and abilities to conduct electricity.

(a) A chlorine atom contains 17 electrons, 18 neutrons and 17 protons.

State the mass number of this chlorine atom.

Give the electronic configuration of this chlorine atom.

Describe what you would see if damp, blue litmus paper is placed into chlorine gas.

Chlorine exists as diatomic molecules.

In a molecule, two chlorine atoms are joined by a covalent bond.

Describe what is meant by a covalent bond.

Explain why chlorine is a gas, rather than a liquid, at room temperature.

When the gas hydrogen chloride, HC l, is dissolved in water, a solution forms. Blue litmus paper dipped in this solution turns red.

State why the litmus paper turns red.

Figure 7 lists the halogens in the order in which they appear in group 7 of the periodic table.

The melting points of four of the halogens are given.

Estimate the melting point of iodine.

_........ °C

Bromine reacts with heated iron.

Give the name of one halogen that would react with iron more vigorously than bromine.

(a) A chlorine atom contains 17 electrons, 18 neutrons and 17 protons.

State the mass number of this chlorine atom.

Give the electronic configuration of this chlorine atom.

Describe what you would see if damp, blue litmus paper is placed into chlorine gas.

Chlorine exists as diatomic molecules.

In a molecule, two chlorine atoms are joined by a covalent bond.

Describe what is meant by a covalent bond.

Explain why chlorine is a gas, rather than a liquid, at room temperature.

When the gas hydrogen chloride, HC l, is dissolved in water, a solution forms. Blue litmus paper dipped in this solution turns red.

State why the litmus paper turns red.