Category: Chemistry

Which of these sets of properties is that of a substance which is molecular?

An element X has the electron configuration 1s²2s²2p². Element Y has the electron configuration 1s²2s²2p⁵. What is the likely formula of the compound of X and Y?

How many shared pairs of electrons are there in an ethene molecule, C₂H₄?

In the formula of water, H-O-H, the lines represent:

(i) shared pairs of electrons

(ii) dative bonds

(iii) covalent bonds

(iv) hydrogen bonds

Typically the molecular compounds of carbon with hydrogen:

(i) are insoluble in water

(ii) form solutions which do not conduct electricity

(iii) are soluble in liquid hydrocarbons

(iv) are denser than water

Which of these elements consist of a giant structure of atoms joined by covalent bonding?

(i) graphite

(ii) sulfur

(iii) diamond

(iv) iodine

An ammonia molecule, NH₃, can react to form an ammonium ion, NH₄⁺. When this happens:

(i) the ammonia molecule forms a bond with a proton

(ii) the ion formed has a tetrahedral shape

(iii) a dative covalent bond forms

(iv) the H-N-H bond angle is 90^o

Which of these compounds consist of molecules which are linear?

(i) water

(ii) beryllium chloride

(iii) sulfur dioxide

(iv) carbon dioxide

Which of these molecules are overall polar?

(i) CH₃Cl

(ii) CH₂Cl₂

(iii) CHCl₃

(iv) CCl₄

A molecule of sulfur hexafluoride, SF₆ is:

Which of these sets of properties is that of an ionic compound?

An element M has two electrons in its outer shell. An element X has seven electrons in its outer shell. What is the likely formula of the compound of X and Y?

What is the electron configuration of an oxide ion?

Typically ionic compounds:

(i) are soluble in water

(ii) conduct electricity when dissolved in water

(iii) are insoluble in liquid hydrocarbons

(iv) decompose when they dissolve in water

During the electrolysis of molten sodium chloride:

(i) sodium metal forms at the negative electrode

(ii) sodium ions are reduced at the cathode

(iii) chloride ions lose electrons at the positive electrode

(iv) chlorine atoms are given off as a gas at the anode

A chloride ion and an argon atom have the same:

(i) number of protons

(ii) number of electrons

(iii) atomic number

(iv) electron configuration

Which of these materials consist of a giant structure of ions?

(i) magnesium oxide

(ii) silicon dioxide

(iii) potassium fluoride

(iv) silicon chloride

How many chloride ions touch each sodium ion in the crystal structure of sodium chloride?

At room temperature, in the crystal lattice of an ionic compound the ions are:

(i) arranged symmetrically

(ii) uncharged

(iii) held together by electrostatic forces

(iv) stationary

Which of these true statements can help to explain why magnesium chloride has a higher melting point than sodium chloride:

(i) magnesium ions are smaller than sodium ion

(ii) magnesium is a less reactive metal than sodium

(iii) the charge on a magnesium ion is double the charge on a sodium ion

(iv) the first ionisation energy is higher for magnesium than for sodium

What is the molar mass of calcium hydroxide?

How many moles of molecules are there in 0.240 g bromine?

What is the mass of 0.00400 mol of sodium hydrogensulfate?

How many sulfate ions are there in 0.01 mol aluminium sulfate?

(The Avogadro constant = 6.02 x 10²³ mol^-1)

What is the empirical formula of an oxide of sodium which contains 74.2% sodium?

What is the molecular formula of a hydrocarbon which consists of 82.8% carbon and has a relative molecular mass estimated in the range 50 and 60.

Calculate the theoretical yield of ethyl ethanoate, CH₃CO₂C₂H₅, when 6.9 g ethanol, C₂H₅OH, reacts with excess ethanoic acid, CH₃CO₂H.

Calculate the volume of oxygen gas formed on strongly heating 3.40 g sodium nitrate which decomposes according to this equation:

2NaNO_3(s) -> 2NaNO_2(s) + O_2(g)

Assume that the volume of 1 mol of any gas is 24 000 cm³ under the conditions of the experiment.

Sodium hydride reacts with water:

NaH_(s) + H₂O_(l) -> NaOH_(aq) + H_2(g)

What is the concentration of a solution of sodium hydroxide formed when 0.600 g sodium hydride reacts with water and the solution is diluted to 100 cm³?

A 20.0 cm³ sample of barium hydroxide solution, Ba(OH)_2(aq), was neutralised by exactly 18.0 cm³ of 0.10 mol dm^-3 hydrochloric acid, HCl_(aq). What was the concentration of the barium hydroxide solution?

How many partially filled orbitals are there in the nitrogen atom?

How many filled orbitals are there in the neon atom?

How many complete shells are there in the zinc atom?

How many complete sub-shells are there in the phosphorus atom?

What is the electronic configuration of sulfide? Enter your answer in the following format 1s2 2s2 etc. (note the space between each sub-shell!) Follow the aufbau order of sub-shell filling.

What is the electronic configuration of bromine? Enter your answer in the following format 1s2 2s2 etc. (note the space between each sub-shell!) Follow the aufbau order of sub-shell filling.

What is the electronic configuration of scandium? Enter your answer in the following format 1s2 2s2 etc. (note the space between each sub-shell!) Follow the aufbau order of sub-shell filling.

What is the electronic configuration of copper? Enter your answer in the following format 1s2 2s2 etc. ((note the space between each sub-shell!) Follow the aufbau order of sub-shell filling.

What is the electronic configuration of sodium? Enter your answer in the following format 1s2 2s2 etc. (note the space between each sub-shell!) Follow the aufbau order of sub-shell filling

What is the electronic configuration of carbon?

Enter your answer in the following format 1s2 2s2 etc. (note the space between each sub-shell!) Follow the aufbau order of sub-shell filling.

The first five ionisation energies of an element in kJ/mol are: 419, 3051, 4412, 5877, 7975. The element is in:

How many p electrons are there in the outer shell of a halogen atom?

What is the electron configuration of sulfur?

Which one of the following is the electron configuration of a group 2 metal atom?

Analysis of a sample of potassium in a mass spectrometer shows that it consists of 93.2% potassium 39 and 6.8% potassium-41. What is the relative atomic mass of potassium?

E represents an atom of an element in the equation: E_(g) -> E⁺_(g) + e^– Which of these statements is/are true:

(i) the element must be a metal

(ii) the enthalpy change for this process is the first ionisation energy of the element

(iii) the element must be a gas at room temperature.

(iv) this process occurs in a mass spectrometer used to analyse the element

The isotopes of an element have the same:

(i) relative atomic mass

(ii) atomic number

(iii) mass number

(iv) electron configuration.

The particle with 3 protons, 4 neutrons and 2 electrons is a:

How many electrons are there in an oxide ion?

How many neutrons are there in an atom of boron with mass number 9 and atomic number 4?

Which of these systems is NOT in a state of dynamic equilibrium?

Each of these statements is true. From which statement is it possible to predict, by application of Le Chatelier's principle that the solubility of sodium hydroxide increases with temperature?

When iron(II) chloride solution mixes with silver nitrate solution some silver metal precipitates and the mixture reaches an equilibrium state.

Fe²⁺_(aq) + Ag⁺_(aq) <=> Fe³⁺_(aq) + Ag_(s)

When the aqueous layer is decanted off, the precipitate of silver redissolves on adding a solution of:

Which of these reactions can be reversed by changing the conditions in a typical advanced chemistry laboratory?

(i) CuSO₄.5H₂O_(s) -> CuSO_4(s) + 5H₂O(l)

(ii) 2Mg_(s) + O_2(g) -> 2MgO_(s)

(iii) NH_3(g) + HCl_(g) -> NH₄Cl_(s)

(iv) CH_4(g) + 2O_2(g) -> CO_2(g) + 2H₂O_(l)

A small crystal of iodine is dissolved in hexane to give a violet coloured solution. After adding an equal volume of colourless, aqueous potassium iodide and shaking, the system reaches equilibrium with the hexane layer floating on top of the aqueous layer. At equilibrium:

(i) the concentrations of iodine in the two layers are the same

(ii) the iodine in the hexane turns brown

(iii) the iodine molecules stop moving between the two layers

(iv) the concentrations in each layer stop changing

Which of these are examples of heterogeneous equilibria?

(i) CaCO_3(s) <=> CaO_(s) + CO_2(g)

(ii) Fe²⁺_(aq) + Ag⁺_(aq) <=> Fe³⁺_(aq) + Ag_(s)

(iii) 3Fe_(s) + 4H₂O_(g) <=> Fe₃O_2(s) + 4H_2(g)

(iv)Br_2(aq) + H₂O(l) <=> HOBr_(aq) + H⁺_(aq) + Br^-_(aq)

For which of these equilibria does a change in pressure have no effect on the yield of substances on the right-hand side of the equation?

(i) CH_4(g) + H₂O_(g) <=> 3H_2(g) + CO_(g)

(ii) 2HI_(g) <=> H_2(g) + I_2(g)

(iii) 2SO_2(g) + O_2(g) <=> 2SO_3(g)

(iv) H₂O_(g) + CO_(g) <=> H_2(g) + CO_2(g)

The reaction of nitrogen with hydrogen to form ammonia is exothermic. Which of these changes increases the proportion of ammonia in an equilibrium mixture of nitrogen, hydrogen and ammonia.

(i) raising the pressure at constant temperature

(ii) raising the temperature at constant pressure

(iii) decreasing the volume at constant temperature

(iv) adding a catalyst

The synthesis of sulfur trioxide takes place at 380 ^oC in the presence of a catalyst made from vanadium(V) oxide.

2SO_2(g) + O_2(g) <=> 2SO_3(g) Standard enthalpy change = -297 kJ mol^-1

Reasons for not choosing a lower temperature are that:

(i) the product condenses to a solid at a lower temperature

(ii) the proportion of SO_3(g) at equilibrium falls if the temperature falls

(iii) the reaction is exothermic

(iv) the catalyst is ineffective at lower temperatures

This is the equilibrium in a solution of bromine in water:

Br_2(aq) + H₂O(l) <=> HOBr_(aq) + H⁺_(aq) + Br^-_(aq)

The orange colour of bromine disappears on adding

(i) sodium bromide

(ii) water

(iii) dilute hydrochloric acid

(iv) sodium hydroxide solution

Using enthalpies of formation Δ_fH, calculate the enthalpy change for the following reaction.

CaCO_3(s) => CaO_(s) + CO_2(g)

Select the data from the 'Selection of Enthalpies of Formation and Combustion'.

If this question was generated from Random Retrieval, this data can also be found in TOOLS>Data Sheets.

Using enthalpies of formation Δ_fH, calculate the enthalpy change for the following reaction.

2NaHCO_3(s) => Na₂CO_3(s) + H₂O_(l) + CO_2(g)

Select the data from the 'Selection of Enthalpies of Formation and Combustion' shown above.

If this question was generated from Random Retrieval, this data can also be found in TOOLS>Data Sheets.

Using enthalpies of formation Δ_fH, calculate the enthalpy change for the following hydration process.

Na₂S₂O_3(s) + 5H₂O_(l) => Na₂S₂O₃•5H₂O_(s)

Select the data from the 'Selection of Enthalpies of Formation and Combustion' shown above.

If this question was generated from Random Retrieval, this data can also be found in TOOLS>Data Sheets.

Using enthalpies of formation Δ_fH, calculate the enthalpy change for the following esterification reaction.

CH₃COOH_(l) + C₂H₅OH_(l) => CH₃COOCH₂CH_3(l) + H₂O_(l)

Select the data from the 'Selection of Enthalpies of Formation and Combustion' shown above.

If this question was generated from Random Retrieval, this data can also be found in TOOLS>Data Sheets.

Using enthalpies of formation Δ_fH, calculate the enthalpy of combustion Δ_cH of ethanol:

C₂H₅OH_(l) + 3O_2(g) => 2CO_2(g) + 3H₂O_(l)

Select the data from the 'Selection of Enthalpies of Formation and Combustion' shown above.

If this question was generated from Random Retrieval, this data can also be found in TOOLS>Data Sheets.

Using enthalpies of combustion Δ_cH, calculate the enthalpy change for the cracking of butane:

C₄H_10(g) => C₂H_6(g) + C₂H_4(g)

Select the data from the 'Selection of Enthalpies of Formation and Combustion' shown above.

If this question was generated from Random Retrieval, this data can also be found in TOOLS>Data Sheets.

Using enthalpies of combustion Δ_cH, calculate the enthalpy change for the hydrogenation of propene:

C₃H_6(g) + H_2(g) => C₃H_8(g)

Select the data from theenthalpies of combustion Δ_cH.

If this question was generated from Random Retrieval, this data can also be found in TOOLS>Data Sheets.

The enthalpy of combustion Δ_cH of butan-1-ol = -2670 kJ mol^-1

Using this figure and data from the 'Selection of Enthalpies of Formation and Combustion' shown above, calculate the enthalpy of formation Δ_fH of liquid butan-1-ol

A Hess Cycle should be drawn to help you calculate this.

If this question was generated from Random Retrieval, this data can also be found in TOOLS>Data Sheets.

Using mean bond dissociation enthalpies, estimate the enthalpy of combustion Δ_cH of liquid ethanol

C₂H₅OH_(l) + 3O_2(g) => 2CO_2(g) + 3H₂O_(l)

The value that you obtain for the enthalpy of combustion Δ_cH of liquid ethanol using mean bond enthalpies is different from the value obtained experimentally, or by using enthalpy of formation Δ_fH of liquid ethanol.

What is the most significant reason for this?

An example of an endothermic change is the:

For which of the following equations is the value for standard enthalpy change equal to the standard enthalpy of formation of sodium chloride?

What are the standard conditions for measuring standard enthalpy changes?

The total heat capacity of a calorimeter is 2000 J K^-1.

The standard enthalpy of combustion of propane is -2200 kJ mol^-1

Calculate the expected temperature rise on heating the calorimeter by burning 0.0500 mol of fuel from a propane burner assuming that all the energy heats the calorimeter.

Take care with units.

The standard enthalpy of combustion of methane is -890 kJ mol^-1. Calculate the energy given out on burning 3.2 g methane.

Hydrazine burns according to this equation: N₂H_4(g) + O_2(g) -> N_2(g) + 2H₂O_(l)

Calculate the standard enthalpy change for the combustion of hydrazine given that the standard enthalpy of formation of hydrazine is +51 kJmol^-1 and of water is -286 kJ mol^-1

Calculate the value of the standard enthalpy change of formation of methane given that the values for standard enthalpy changes of combustion are -890 kJ mol^-1 for methane, -393 kJ mol^-1 for carbon and -286 kJ mol^-1 for hydrogen gas.

The energy needed to atomise 1 mol of gaseous ethene, C₂H₄ is 2087 kJ mol^-1. Calculate the average bond enthalpy for a C-H bond given that the bond enthalpy for the C=C bond is +347 kJ mol^-1.

Calculate the enthalpy change for the formation of one mole of hydrogen chloride gas from its elements given these average bond enthalpies: H-H bond enthalpy = 435 kJ mol^-1, Cl-Cl bond enthalpy = 243 kJ mol^-1 and H-Cl bond enthalpy = 432 kJ mol^-1

The standard enthalpy change of formation of N₂O_(g) is +82 kJ mol^-1. This shows that

Which of the following properties increase from left to right across the series: AgCl - AgBr - AgI?

(i) intensity of colour

(ii) solubility in ammonia solution

(iii) ease of oxidation to the halogens

(iv) solubility in aqueous ammonia

Which of the following increase from left to right across the series F₂ - Cl₂ - Br₂?

(i) covalent radius of the atoms

(ii) electronegativitiy

(iii) boiling point

(iv) strength as an oxidising agent

The total O.N. of all the halogen atoms in these compounds ClO^-, BrO^-, ICl, XeF₄ is:

A solution of Br₂ and KI were mixed. Then shaken with cyclohexane. Which is correct?

(i) the bromine is reduced

(ii) the cyclohexane layer goes brown

(iii) the cyclohexane layer goes purple

(iv) the iodine is reduced

Chlorine disproportionates when it reacts with:

The oxidising agent used to extract bromine from sea water in a displacement reaction is:

Iodine oxidises thiosulfate ions, S₂O₃^2 -, to S₄O₆^2- . What is the oxidation number (O.N.) change for each sulfur atom?

When chlorine reacts with cold, aqueous sodium hydroxide the ions formed are:

In which of these molecules do the intermolecular forces arise largely from attractions between temporary dipoles?

The electron configuration of a chloride ion is: