Category: Chemistry

4.89g of potassium hydroxide was dissolved in deionised water and made up to 250cm³ in a volumetric flask.

20.0cm³ samples were titrated against hydrochloric acid solution of concentraion 0.300 mol dm^-3.

A mean titre of 18.85cm³ of hydrochloric acid solution was obtained.

Calculate the percentage purity, by mass, of the original solid. (Don't include the % symbol and give answer to 1 decimal place!)

2.79g of sodium carbonate was dissolved in deionised water and made up to 250cm³ in a volumetric flask.

20.0cm³ samples were titrated against hydrochloric acid solution of concentraion 0.350 mol dm^-3.

A mean titre of 11.80cm³ of hydrochloric acid solution was obtained.

Calculate the percentage purity, by mass, of the original solid. (Don't include the % symbol and give answer to 1 decimal place!)

1.04g of sodium hydroxide was dissolved in deionised water and made up to 100cm³ in a volumetric flask.

10.0cm³ samples were titrated against hydrochloric acid solution of concentraion 0.100 mol dm^-3.

A mean titre of 22.10cm³ of hydrochloric acid solution was obtained.

Calculate the percentage purity, by mass, of the original solid. (Don't include the % symbol and give answer to 1 decimal place!

1.98g of lithium carbonate was dissolved in deionised water and made up to 100cm³ in a volumetric flask.

25.0cm³ samples were titrated against hydrochloric acid solution of concentraion 0.500 mol dm^-3.

A mean titre of 25.35cm³ of hydrochloric acid solution was obtained.

Calculate the percentage purity, by mass, of the original solid. (Don't include the % symbol and give answer to 1 decimal place!)

1g of sodium hydroxide was dissolved in deionised water and made up to 100cm³ in a volumetric flask.

25.0cm³ samples were titrated against nitric acid solution of concentraion 0.200 mol dm^-3.

A mean titre of 28.25cm³ of nitric acid solution was obtained.

Calculate the percentage purity, by mass, of the original solid. (Don't include the % symbol and give answer to 1 decimal place!)

Calculate the pH of a solution created by the addition of 30.0cm³ 0.100 mol dm^-3 lithium hydroxide solution to 35.0 cm³ 0.100 mol dm^-3 hydrobromic acid solution.

Remember to give your answer to 3 sig.fig.

By titration, it was found that an average titre of 19.95cm³ of 0.180 mol dm^-3 solution of nitric acid was required to just neutralise a 10.00 cm³ sample of sodium carbonate solution. Calculate the concentraion of the sodium carbonate solution.

The equation for the reaction is

2HNO_3(aq)+Na₂CO_3(aq)=>2NaNO_3(aq)+H₂O_(aq)+CO_2(g)

By titration, it was found that an average titre of 19.75cm³ of 0.200 mol dm^-3 solution of hydrochloric acid was required to just neutralise a 10.00 cm³ sample of lithium hydroxide solution. Calculate the concentraion of the lithium hydroxide solution.

The equation for the reaction is

LiOH_(aq)+HCl_(aq)=>LiCl_(aq)+H₂O_(aq)

By titration, it was found that an average titre of 22.25cm³ of 0.100 mol dm^-3 solution of hydrochloric acid was required to just neutralise a 20.00 cm³ sample of lithium hydroxide solution. Calculate the concentraion of the lithium hydroxide solution.

The equation for the reaction is

LiOH_(aq)+HCl_(aq)=>LiCl_(aq)+H₂O_(aq)

By titration, it was found that an average titre of 20.00cm³ of 1.20 mol dm^-3 solution of nitric acid was required to just neutralise a 25.00 cm³ sample of potassium hydroxide solution. Calculate the concentraion of the potassium hydroxide solution.

The equation for the reaction is

KOH_(aq)+HNO_3(aq)=>KNO_3(aq)+H₂O_(aq)

What volume (in cm³) of deionised water would you need to add to 50.0cm³ of ammonia solution to dilute it from a concentration of 10.0 mol dm^-3 into a concentration of 1.00 mol dm^-3?

Calculate the concentration of lithium hydroxide in a solution of volume 2.20dm³ that contains 89.0 g of lithium hydroxide

Li=6.9 O=16.0 H=1.0

Calculate the concentration of aluminium sulfate in a solution of volume 250.00cm³ that contains 4.00 g of aluminium sulfate

S=32.1 Al=27.0 O=16.0

Calculate the concentration of barium nitrate in a solution of volume 21.95cm³ that contains 0.670 g of barium nitrate

Ba=137.3 N=14.0 O=16.0

Calculate the concentration of CuSO₄ in a solution of volume 250.00cm³ that contains 20.0 g of CuSO₄

S=32.1 Cu=63.5.0 O=16.0

Calculate the concentration of sodium chloride in a solution of volume 4.25dm³ that contains 58.5 g of sodium chloride

Na=23.0 Cl=35.5

Calculate the volume of solution in dm³ that would contain 0.150 mol of chlorate (I) ions if the concentration of the solution is 0.300 mol dm^-3

Calculate the volume of solution in dm³ that would contain 5.00 mol of glucose if the concentration of the solution is 2.50 mol dm^-3

Calculate the number of moles of potassium chloride in a solution of volume 0.90 dm³ and a concentration of 0.0125 mol dm^-3

Calculate the number of moles of NaCl in a solution of volume 250.00 cm³ and a concentration of 0.150 mol dm^-3

Calculate the volume of gas (in cm³) of 0.175 mol of hydrogen if the gas is at a temperature of 527^oC and a pressure of 1000000Pa

Calculate the volume of gas (in cm³) of 0.0500 mol of hydrogen if the gas is at a temperature of 0^oC and a pressure of 505000Pa

Calculate the temperature of a sample of butane (in ^oC) if 0.110 mol of butane has a volume of 879cm³ and is at a pressure of 700kPa

Calculate the temperature of a sample of gaseous ammonia (in K) if 0.2050 mol of gaseous ammonia has a volume of 4200cm³ and is at a pressure of 750000Pa

Calculate the number of moles of gas present at r.t.p in 700 cm³ of butane.

Calculate the number of moles of gas present at r.t.p in 240 cm³ of fluorine.

Calculate the number of moles of gas present at r.t.p in 1900 cm³ of gaseous ammonia.

Calculate the number of moles of gas present at r.t.p in 6.00 m³ of sulfur hexafluoride.

Calculate the number of moles of gas present at r.t.p in 96.0 dm³ of methane.

0.277g of gas was collected. The volume of gas was recored as 505 cm³ at a temperature of 400 K and a pressure of 130000Pa

Determine the relative formula mass of the chemical.

Calculate the relative molecular mass (formula mass) of lithium carbonate, Li₂CO₃

Calculate the number of moles of calcium carbonate if you have 60.0 g of calcium carbonate

Ca=40.1 C=12.0 O=16.0

Calculate the number of moles of KHCO₃ if you have 25.0 g of KHCO₃

K=39.1 H=1.0 C=12.0 O=16.0

Calculate the number of moles of N₂ if you have 28.0 g of N₂

N=14.0

Calculate the mass of anydrous copper (II) sulfate that you would have if you had 6.10 mol of anydrous copper (II) sulfate

S=32.1 Cu=63.5 O=16.0

Calculate the mass of iodine that you would have if you had 0.0500 mol of iodine

I=126.9

Calculate the mass of Cl₂ that you would have if you had 4.00 mol of Cl₂

Cl=35.5

Calculate the mass of H₂S that you would have if you had 6.00 mol of H₂S

S=32.1 H=1.0

Calculate the mass of P₄ that you would have if you had 3.00 mol of P₄

P=31.0

Calculate the mass of NaOH that you would have if you had 0.100 mol of NaOH

Na=23.0 O=16.0 H=1.0

Zinc metal reacts with hydrochloric acid

Zn+ 2HCl=>ZnCl₂+H₂

What volume of 2mol dm^-3 HCl will react with 2 mol of Zn?

P₄O₁₀+ H₂O => H₃PO₄

NaHCO₃ => Na₂CO₃ + CO₂ + H₂O

A compound with empirical formula CH₂ has a relative molecular mass of 84. Which of the following is the molecular formula of the compound?

Fe(OH)₂

Ca(NO₃)₂

Work out the formula of each of the following ionic compounds. Use the data sheet ‘Names & Formulae of Some Common Ions’

Use upper case letter I for roman numerals e.g. (II)

Formulae are Case Sensitive.

Use regular numbers in formulae e.g. H2O not H₂O

lithium bromide

0.100mol of X atoms has a mass of 15.2g. The element is a mixture of two isotopes in equal amounts. One of these is ¹⁵¹X. What is the mass number of the other isotope?

Calculate the mass of 0.00200 mol of sodium atoms

Identify the element (write the symbol) if an atom of X is four times as heavy as an atom of carbon-12.

What are the products of the acid hydrolysis of methyl propanoate?

Which of the following molecules would you predict to be the least nucleophilic?

In which of these organic compounds are all the bonds non-polar?

(i) 1-bromobutane

(ii) butene

(iii) butan-2-ol

(iv) butane

Which of these compounds have E/Z isomers?

(i) pent-2-ene,

(ii) 2-methylpent-2-ene,

(iii) 1,2-dichloropropene,

(iv) hex-1-ene

Consider the following equilibrium:

N_2(g) + O_2(g) <=>2NO_(g)

1.80 x 10^-3 mol of N₂ was mixed with 2.40 x 10^-3 mol of O₂ and 7.20 x 10^-3 mol of NO and the mixture sealed in a container. The mixture was left until no further observable change in composition took place. At this point, 4.80 x 10^-3 mol of O₂ was present in the mixture.

Calculate the value of the mole fraction of O₂ present in the mixture under these conditions.

Which of the following are examples of heterogeneous equilibria?

(i) CaCO_3(s) <=> CaO_(s) + CO_2(g)

(ii) 2CrO₄^2-_(aq) + 2H⁺_(aq) <=> Cr₂O₇^2-_(aq) + H₂O_(l)

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

(iv) Co²⁺_(aq) + 6NH_3(aq) <=> [Co(NH₃)₆]²⁺_(aq)

Look at the chemical equation below.

CH_4(g) + H₂O_(g)=> CO_(g)+ 3H_2(g)

Using your answers to Questions 6 and 7, calculate the Gibbs Energy change ΔG, for the process if it is carried out in a reactor vessel at 1500^oC.

If this question is from a Random Retrieval, you can also carry out this calculation by first working out values for ΔS^Ɵ and ΔH^Ɵ by selecting the appropriate data from the ‘Selection of Thermodynamic Data’ in TOOLS.

Look at the chemical equation below.

CH_4(g) + H₂O_(g)=> CO_(g)+ 3H_2(g)

Calculate the temperature at which this process just becomes feasible.

If this question is from a Random Retrieval, you can also carry out this calculation by first working out values for ΔS^Ɵ and ΔH^Ɵ by selecting the appropriate data from the ‘Selection of Thermodynamic Data’ in TOOLS.

Using oxidation numbers (states) work out the ratio of the species in the following half-equation.

ClO^- + H⁺ + e^- => Cl^- + H₂O

What is the value of E^ϴcell/V observed for a cell constructed from the following half-cells?

Mg²⁺_(aq) + 2e^- <=> Mg_(s) E^ϴcell/V = -2.37

Ag⁺_(aq) + e^- <=> Ag_(s) E^ϴcell/V = +0.80

What is the value of E^ϴcell/V observed for a cell constructed from the following half-cells?

V³⁺_(aq) + e^- <=> V²⁺_(aq) E^ϴcell/V = -0.26

VO₂⁺_(aq) + 2H⁺_(aq) + e^- <=> VO²⁺_(aq) + H₂O_(l) E^ϴcell/V = +1.00

Using your half-equations from questions 10 & 11, balance the REDOX equation below.

S₂O₃^2- + I₂ => S₄O₆^2- + I^-

Select the integers that represent the ratio of species in the overall balanced REDOX equation.

If this question appears in a Random Retrieval quiz, you would be best constructing separate half-equations for the species that is oxidised and the species that is reduced prior to working out the overall REDOX equation.

In an EDTA complex with a copper(II) ion

(i) there are six ligand molecules,

(ii) there are four dative bonds between oxygen atoms and the metal ion,

(iii) the overall charge on the complex ion is zero,

(iv) there are two dative bonds between nitrogen atoms and the metal ion

What enthalpy change is represented by the following equation?

S^-_(g) + e^-=> S^2-_(g)

Consider the following equilibrium:

3Fe_(s) + 4H₂O_(g) Fe₃O_4(s)+ 4H_2(g)

40.0 g of iron wool was placed in a vessel of volume 2.00 dm³. The iron was exposed to 20.0 mol of high pressure steam and the system allowed to settle to equilibrium. At equilibrium, 0.250 mol of hydrogen was found in the vessel. The gauge on the pressure vessel read 1 000 kPa. The volume of iron wool was insignificant.

Calculate the value of K_p (no units) under these conditions.

Consider the following equilibrium:

N_2(g) + O_2(g) <=>2NO_(g)

5.00 x 10^-3 mol of N₂ was mixed with 4.00 x 10^-3 mol of O₂ and 11.0 x 10^-3 mol of NO and the mixture sealed in a container. The volume of the container was 0.500 dm³. The mixture was left to form a stable equilibrium. At this point, 9.00 x 10^-3 mol of NO was present in the mixture. The pressure was recorded as 45000 kpa

Calculate the value of K_p (no units) under these conditions.

Consider the following equilibrium for the reaction that generates hydrogen for use in the Haber-Bosch Process:

CH_4(g) + H₂O_(g) <=>CO_(g) + 3H_2(g)

140 mol of CH₄ was mixed with 100 mol of H₂O and the mixture given time to reach equilibrium. At this point, 240 mol of H₂ was present in the mixture.

Calculate the value of the mole fraction of CH₄ present in the mixture under these conditions.

Consider the following reaction.

O_3(g) + Cl_(g) => O_2(g)+ ClO_(g)

The rate equation was found, by experiment.

rate = k [O₃] [Cl]

Which of the following statements is/are true?

(i) Doubling [O₃] has no effect on the rate of the reaction

(ii) The mechanism probably has more than one step

(iii) There is one particle involved in the slowest step

(iv) The mechanism probably has only one step

Consider the following reaction:

2NO_(g) + O_2(g) => 2NO_2(g)

The rate equation was found, by experiment:

rate = k [NO_(g)]² [O_2(g)]

Which of the following statements is/are true?

(i) Doubling [O₂] has no effect on the rate of the reaction

(ii) Doubling both [NO] and [O₂] quadruples the rate of the reaction

(iii) Tripling [NO] triple the rate of the reaction

(iv) The mechanism may have only one step

A Maxwell-Boltzman plot shows the distribution of molecular energies in a sample of gas at a 300K. The curve showing the distribution at 310K:

(i) has a wider spread,

(ii) has a higher peak,

(iii) has the peak shifted to the right,

(iv) has a larger area under the curve.

How many peaks would you expect to see in the ¹³C spectrym of 2,5-dimethyltetrahydrofuran?

NOT ON OCR SPEC. Hint: Esters can be hydrolysed and the initial stage in the mechanism is nucleophilic attack using an oxygen lone pair of the water molecule. RO^- is the leaving group and becomes ROH.

¹⁸O is a ‘radiolabelled oxygen’.

The reaction of ethyl ethanoate with H₂¹⁸O produces:

Step 1:

Step 8:

The monomer which polymerises to form a plastic which has a smooth, slippery surface and is used to give cooking utensils a non-stick surface is:

What is the reagent used to convert benzene to nitrobenzene?

Heating methylbenzene under reflux with excess, alkaline potassium manganate(VII) which is a strong oxidising agent produces:

The product of the reaction of ethanoic acid and ammonia at room temperature is:

The hydride ion, H^-, is:

(i) a reducing agent

(ii) a nucleophile

(iii) a base

(iv) a free radical

Which of these aldehydes are isomers of pentan-2-one?

(i) pentanal

(ii) 2-methylbutanal

(iii) 3-methylbutanal

(iv) 2,2-dimethylbutanal

What is the product when methanol and propanoic acid are mixed and warmed in the presence of a few drops of acid?

Which of these alcohols is a tertiary alcohol?

(i) CH₃CH₂CHOHCH₃

(ii) CH₃CH(CH₃)CHOHCH₃

(iii) CH₃C(CH₃)₂CH₂CHOHCH₃

(iv) (CH₃)₃COH

Choose one of the following options:

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.

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

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

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.

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

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?

Which of these acids is only slightly ionised in aqueous solution?

(i) hydrochloric acid

(ii) nitric acid

(iii) sulfuric acid

(iv) ethanoic acid

Which of these changes are redox reactions?

(i) NaCl_(s) + H₂SO_4(l) -> HCl_(g) + NaHSO_4(s)

(ii) NH_3(g) + HCl_(g) -> NH₄Cl_(s)

(iii) CaCO_3(s) -> CaO_(s) + CO_2(g)

(iv) 2HBr_(g) + H₂SO_4 (l) -> Br_2(l) + SO_2(g) + 2H₂O_(l)

The oxidation number of sulfur in sulfuric acid, H₂SO₄, is:

In a titration, 25 cm³ of 0.100 mol dm^-3 potassium hydroxide was neutralised by 12.5 cm³ dilute nitric acid. What was the concentration of the nitric acid?

Dilute hydrochloric acid reacts with:

(i) zinc to form zinc chloride and hydrogen

(ii) copper(II) oxide to form copper(II) chloride and water

(iii) zinc carbonate to form zinc chloride, carbon dioxide and water

(iv) copper to form copper(II) chloride and hydrogen

What is the temperature of a 12dm³ sample of gas that contains 7g of nitrogen if it is held at a pressure of 300kPa pressure given that the value of the gas constant R = 8.314 J mol^-1K^-1?:

The pressure of a gas results from:

Steel and graphite are similar in that they both.

(i) conduct electricity

(ii) are dark grey/black when powdered

(iii) can have high tensile strength

(iv) are brittle

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

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?

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

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?

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.

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.

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.

Which of the following increase from left to right along the series Mg - Ca - Sr - Ba?

(i) the thermal stability of the nitrates

(ii) the thermal stability of the carbonates

(iii) the solubility of the hydroxides in water

(iv) the solubility of the sulfates in water

The reaction of calcium with water produces:

What is the oxidation number of CARBON in methanoic acid

HCOOH

What is the oxidation number of CARBON in

CH₄

In the periodic table the elements are arranged in order of:

(i) atomic number

(ii) mass number

(iii) number of protons in the nucleus

(iv) number of protons and neutrons in the nucleus.

Choose one of the following options:

Choose one of the following options:

There are two main peaks in the infra-red spectrum of carbon dioxide.

This shows that carbon dioxide molecules:

Adding a compound X, C₄H₁₀O, drop by drop to a hot acidic solution of potassium dichromate(VI) and allowing the product to distil off as it forms, produces a compound which gives a silver mirror with Tollens solution. This shows that X could be:

(i) CH₃CH₂CH₂CH₂OH

(ii)CH₃CH₂CHOHCH₃

(iii)CH₃CH(CH₃)CH₂OH

(iv) CH₃CH₂OCH₂CH₃

Which of these alcohols is a tertiary alcohol?

(i) CH₃CH₂CHOHCH₃

(ii) CH₃CH(CH₃)CHOHCH₃

(iii) CH₃C(CH₃)₂CH₂CHOHCH₃

(iv) (CH₃)₃COH

Why is ethanol a liquid while propane is a gas? (Relative atomic masses: C = 12, H = 1, O = 16)

Which of these alkenes shows E/Z isomerism?

How many monosubstitution products can be formed when butane reacts with chlorine?

One mole of an alkane needs 8 moles of oxygen for complete combustion. What is the molecular formula of the alkane?

What is the H-C-H bond angle in ethene?

Which reagent can be used to convert butan-1-ol to but-1-ene?

How many functional group isomers of C₄H₈ are there?

Choose one of the following options:

What is the oxidation number of NITROGEN in

NH₃

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

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 bond angle found in SO₄^2-?

What is/are the bond angle(s) found in iodine trifluoride?

(i) 104.5^o

(ii) 120^o

(iii) 107^o

(iv) 90^o

Typically metal elements, unlike most solid non-metal elements:

(i) are shiny

(ii) conduct electricity

(iii) bend and stretch without breaking

(iv) have low tensile strength.

Step 6:

Step 5:

NOT ON OCR SPEC. Hint: Esters can be hydrolysed and the initial stage in the mechanism is nucleophilic attack using an oxygen lone pair of the water molecule. RO^- is the leaving group and becomes ROH.

¹⁸O is a ‘radiolabelled oxygen’.

The reaction of ethyl ethanoate with H₂¹⁸O produces:

A Maxwell-Boltzman plot shows the distribution of molecular energies in a sample of gas at a 300K. The curve showing the distribution at 310K:

(i) has a wider spread,

(ii) has a higher peak,

(iii) has the peak shifted to the right,

(iv) has a larger area under the curve.

For which of these changes is the enthalpy change the standard enthalpy of atomisation of bromine?

Which first-row d-block metal forms hydrated ions in the +3 state which undergo a ligand exchange reaction to form a deep red complex ion with thiocyanate ions, SCN^-.

Using oxidation numbers (states) work out the ratio of the species in the following half-equation.

S₂O₃^2- => S₄O₆^2- + e^-

Work out the ratio of the species in the following half-equation.

Br^- => Br₂ + e^-

Using your half-equations from questions 4 & 5, balance the REDOX equation below.

BrO₃^- + H⁺ + C₂O₄^2- => CO₂ + Br^- + H₂O

Select the integers that represent the ratio of species in the overall balanced REDOX equation.

If this question appears in a Random Retrieval quiz, you would be best constructing separate half-equations for the species that is oxidised and the species that is reduced prior to working out the overall REDOX equation.

Work out the ratio of the species in the following half-equation.

I₂ + e^- => I^-

I₂ = [1] 1 [2] 2 [3] 3 [4] 4 [5] 5 [6] 6

e^- = [7] 1 [8] 2 [9] 3 [10] 4 [11] 5 [12] 6

I^- = [13] 1 [14] 2 [15] 3 [16] 4 [17] 5 [18] 6

What is the concentration of a solution of sodium hydroxide that is made by dissolving 20.0g of the solid in water and making the solution up to 250 cm³? (Relative atomic masses: Na = 23, O = 16, H = 1)

Which of these gases behaves very much like an ideal gas at room temperature and pressure?

(i) helium

(ii) oxygen

(iii) hydrogen

(iv) butane

Which of these elements has a relatively low boiling point (below 500 ^oC)?

Zinc conducts electricity at room temperature because:

(i) the metal is solid

(ii) zinc is a d-block element

(iii) the atoms in the structure are in contact with each other

(iv) the bonding electrons are delocalised

What is the bond angle found in SO₄^2-?

What is the bond angle found in ammonia?

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

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?

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

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