## A. The equation for the reaction of strontium hydroxide with hydrochloric acid

a. The equation for the reaction of strontium hydroxide with hydrochloric acid is shown below.

Sr(OH)2 + 2HCl SrCl2 + 2H2O

25.0 cmof a solution of strontium hydroxide was exactly neutralised by 15.00 cm3 of 0.100 mol dm–3 hydrochloric acid. Calculate the concentration, in mol dm–3, of the strontium hydroxide solution.

b. 20.0 cm3 of a 0.400 mol dm–3 solution of sodium hydroxide was exactly neutralised by 25.25 cm3 of sulfuric acid. Calculate the concentration, in mol dm–3, of the sulfuric acid. The equation for the reaction is:

H2SO+ 2NaOH → Na2SO4 + 2H2O

## Zirconium, Zr, and hafnium, Hf, are metals. An isotope of zirconium has

Zirconium, Zr, and hafnium, Hf, are metals. An isotope of zirconium has 40 protons and 91 nucleons.

a. i. Write the isotopic symbol for this isotope of zirconium.
ii. How many neutrons are present in one atom of this isotope?

b. Hafnium ions, 180 72 Hf 2+, are produced in a mass spectrometer. How many electrons are present in one of these hafnium ions?

c. The subatomic particles present in zirconium and hafnium are electrons, neutrons and protons. A beam of protons is fired into an electric field produced by two charged plates, as shown in the diagram.

i. Describe how the beam of protons behaves when it passes through the gap between the charged plates. Explain your answer.
ii. Describe and explain what happens when a beam of neutrons passes through the gap between the charged plates.

## A. Sodium reacts with excess oxygen to form sodium peroxide, Na2O2.2Na +

a. Sodium reacts with excess oxygen to form sodium peroxide, Na2O2.

2Na + O2 → Na2O2

Calculate the maximum mass of sodium peroxide formed when 4.60 g of sodium is burnt in excess oxygen. (Ar values: Na = 23.0, O = 16.0)

b. Tin(IV) oxide is reduced to tin by carbon. Carbon monoxide is also formed.

SnO2 + 2C → Sn + 2CO

Calculate the mass of carbon that exactly reacts with 14.0 g of tin(IV) oxide. Give your answer to 3 significant figures.
(Ar values: C = 12.0, O = 16.0, Sn = 118.7)

## The table below shows the 1st ionisation energies, ΔHi1, in kJ mol–1,

The table below shows the 1st ionisation energies, ΔHi1, in kJ mol–1, of the elements in Period 3 of the Periodic Table.

a. Explain why there is a general increase in the value of ΔHi1 across the period.

b. Explain why aluminium has a lower value of ΔHi1 than magnesium.

c. Write the electronic configuration for argon (Z = 18) using 1s2 notation.

d. Copy and complete the diagram below for the 15 electrons in phosphorus by
i. Adding labels for the other subshells.
ii. Showing how the electrons are arranged..

e. Predict a value for the 1st ionisation energy for potassium, which has one more proton than argon.

## The 1st ionisation energies of several elements with consecutive atomic numbers are

The 1st ionisation energies of several elements with consecutive atomic numbers are shown in the graph below. The letters are not the symbols of the elements.

a. Which of the elements A to I belong to Group 1 in the Periodic Table? Explain your answer.

b. Which of the elements A to I could have the electronic configuration 1s2s2 2p6 3s2?

c. Explain the rise in 1st ionisation energy between element E and element G.

d. Estimate the 1st ionisation energy of element J.

e. The successive ionisation energies of element a are shown in the sketch graph.

What information does this graph give about how the electrons are arranged in shells for element A?

## A. i. What do you understand by the term relative atomic mass?ii.

a. i. What do you understand by the term relative atomic mass?

ii. A sample of boron was found to have the following % composition by mass:

Calculate a value for the relative atomic mass of boron. Give your answer to 3 significant figures.

b. Boron ions, B3+, can be formed by bombarding gaseous boron with high-energy electrons in a mass spectrometer. Deduce the number of electrons in one B3+ ion.

c. Boron is present in compounds called borates.

i. Use the Ar values below to calculate the relative molecular mass of iron(III) borate, Fe(BO2)3. (Ar values: Fe = 55.8, B = 10.8, O = 16.0)
ii. The accurate relative atomic mass of iron, Fe, is 55.8. Explain why the accurate relative atomic mass is not a whole number.

## A. The first ionisation energies of four consecutive elements in the Periodic

a. The first ionisation energies of four consecutive elements in the Periodic Table are: sodium = 494 kJ mol–1

magnesium = 736 kJ mol–1

aluminium = 577 kJ mol–1

silicon = 786 kJ mol–1
i. Explain the general increase in ionisation energies from sodium to silicon.

ii. Explain why aluminium has a lower first ionisation energy than magnesium.

b. The first ionisation energy of fluorine is 1680 kJ mol–1 whereas the first ionisation energy of iodine is 1010 kJ mol–1. Explain why fluorine has a higher first ionisation energy than iodine despite it having a smaller nuclear charge.

## This question is about two transition metals, hafnium (Hf) and zirconium (Zr).a.

This question is about two transition metals, hafnium (Hf) and zirconium (Zr).

a. Hafnium forms a peroxide whose formula can be written as HfO3.2H2O. Use the Ar values below to calculate the relative molecular mass of hafnium peroxide.
(Avalues: Hf = 178.5, H = 1.0, O = 16.0)

b. A particular isotope of hafnium has 72 protons and a nucleon number of 180. Write the isotopic symbol for this isotope, showing this information.

c. The mass spectrum of zirconium is shown below.

i. Use the information from this mass spectrum to calculate the relative atomic mass of zirconium. Give your answer to 3 significant figures.
ii. High-resolution mass spectra show accurate relative isotopic masses. What do you understand by the term relative isotopic mass?

## Solid sodium carbonate reacts with aqueous hydrochloric acid to form aqueous sodium

Solid sodium carbonate reacts with aqueous hydrochloric acid to form aqueous sodium chloride, carbon dioxide and water.

Na2CO+ 2HCl → 2NaCl + CO+ H2O

a. Rewrite this equation to include state symbols.

b. Calculate the number of moles of hydrochloric acid required to react exactly with 4.15 g of sodium carbonate.
(Ar values: C = 12.0, Na = 23.0, O = 16.0)

c. Define the term mole.

d. An aqueous solution of 25.0 cm3 sodium carbonate of concentration 0.0200 mol dm–3 is titrated with hydrochloric acid. The volume of hydrochloric acid required to exactly react with the sodium carbonate is 12.50 cm3.
i. Calculate the number of moles of sodium carbonate present in the solution of sodium carbonate.
ii. Calculate the concentration of the hydrochloric acid.

e. How many moles of carbon dioxide are produced when 0.2 mol of sodium carbonate reacts with excess hydrochloric acid?

f. Calculate the volume of this number of moles of carbon dioxide at r.t.p. (1 mol of gas occupies 24 dm3 at r.t.p.)

## Hydrocarbons are compounds of carbon and hydrogen only. Hydrocarbon Z is composed

Hydrocarbons are compounds of carbon and hydrogen only. Hydrocarbon Z is composed of 80% carbon and 20% hydrogen.

a. Calculate the empirical formula of hydrocarbon Z.
(Avalues: C = 12.0, H = 1.0)

b. The molar mass of hydrocarbon Z is 30.0 g mol–1. Deduce the molecular formula of this hydrocarbon.

c. When 50 cm3 of hydrocarbon y is burnt, it reacts with exactly 300 cm3 of oxygen to form 200 cm3 of carbon dioxide. Water is also formed in the reaction. Deduce the equation for this reaction. Explain your reasoning.

d. Propane has the molecular formula C3H8. Calculate the mass of 600 cmof propane at r.t.p. (1 mol of gas occupies 24 dm3 at r.t.p.) (Avalues: C = 12.0, H = 1.0)