Isotopes and relative atomic mass

This question is about vanadium and some of its compounds.

State the block in the Periodic Table that contains vanadium.

Suggest why vanadium can be pulled into thin wires.

Vanadium(V) oxide is a catalyst in the Contact process.

Give two equations to show how vanadium(V) oxide acts as a catalyst in this process.

Equation 1

Equation 2

Table 6 shows some electrode half-equations and their standard electrode potentials.

Sn reduces VO₂⁺ in acidic solution.

Use the data in Table 6 to deduce an overall equation for the reaction that occurs.

Vanadium(III) sulfate is a pale yellow solid at room temperature.

Explain why vanadium(III) sulfate has a high melting point.

When vanadium(III) sulfate dissolves in water, the vanadium-containing species formed is acidic.

Give an equation to show how vanadium(III) sulfate dissolves in water to form the acidic vanadium-containing species.

Explain why the vanadium-containing species is acidic.

Equation

Compound Q is found in crude oil and has the molecular formula C₃₃H₃₄N₄VO₄

A sample of Q is ionised by electrospray ionisation in a time of flight (TOF) mass spectrometer. The spectrum produced shows that the

Give an equation to show how Q is ionised using electrospray ionisation.

Determine the m / z value of the molecular ion formed in this ionisation process.

Equation

A sample of vanadium contains only⁴⁹V and⁵¹V

The relative atomic mass of vanadium in this sample is 50.97

Calculate the percentage abundance of⁵¹V in this sample.

A sample of UF₆ consists of molecules containing¹⁹F and either²³⁵U or²³⁸U atoms.

The relative molecular mass of the sample is 351.43

What is the percentage abundance of²³⁵UF₆ in the sample?

This question is about atomic structure.

In 1897 JJ Thomson discovered the electron. He suggested that atoms were positively charged spheres with electrons embedded within them.

Figure 1 represents an atom using Thomson’s model.

Suggest the identity of this atom.

Give two differences between the modern model of an atom and the Thomson model of an atom.

Tellurium has a relative atomic mass of 127.6 Iodine has a relative atomic mass of 126.9

Define relative atomic mass.

Suggest one property of tellurium that justifies its position before iodine in the modern Periodic Table.

A sample of tellurium is analysed in a time of flight (TOF) mass spectrometer using electron impact ionisation.

Give an equation, including state symbols, for this ionisation.

In the TOF mass spectrometer an ion of an isotope of tellurium, with mass number y, travels along a 1.25 m flight tube with a kinetic energy of 1.88 x 10^–12 J

The ion takes 3.00 x 10^–7 s to reach the detector.

KE = kinetic energy / J m = mass / kg

Calculate the mass, in g, of 1 mole of these tellurium ions.

Use your answer to suggest the mass number y of the tellurium isotope.

The Avogadro constant, L = 6.022 × 10²³ mol^–1

Tellurium has several other isotopes. Two of these isotopes are¹²⁶Te and¹²⁴Te A different sample of tellurium is analysed using a TOF mass spectrometer.

Which statement about kinetic energy (KE) is correct?

Tick (✓) one box.

Which row contains two species with different numbers of electrons?

This is a question about time of flight (TOF) mass spectrometry.

Give the equation, including state symbols, for the formation of Sr⁺ ions from Sr atoms by electron impact.

A sample of strontium is analysed by TOF mass spectrometry. The sample is ionised using electron impact.

The ions are accelerated to have a kinetic energy (KE) of 7.02 × 10^–20 J An ion takes 9.47 × 10^–4 s to travel along a 95.0 cm flight tube.

Use the information given to deduce the mass number of this ion.

The Avogadro constant, L = 6.022 × 10²³ mol⁻¹

Explain how the ions are detected in the TOF mass spectrometer.

State how the relative abundance of the ions is determined.

How ions are detected

How relative abundance is determined

A sample of strontium contains three isotopes,⁸⁶Sr,⁸⁷Sr and⁸⁸Sr

Calculate the percentage abundance of⁸⁷Sr in this sample.

Use your answer to deduce the relative atomic mass (A_r) of the sample. Give your answer to 1 decimal place.

Electrospray ionisation is used instead of electron impact for the ionisation of a protein in a mass spectrometry experiment.

Suggest why.

Which row shows the number of each fundamental particle in one²⁵Mg²⁺ ion?

Rhenium has an atomic number of 75

Define the term relative atomic mass.

The relative atomic mass of a sample of rhenium is 186.3

Table 2 shows information about the two isotopes of rhenium in this sample.

Calculate the relative isotopic mass of the other rhenium isotope. Show your working.

State why the isotopes of rhenium have the same chemical properties.

A sample of rhenium is ionised by electron impact in a time of flight (TOF) mass spectrometer.

A¹⁸⁵Re⁺ ion with a kinetic energy of 1.153 × 10⁻¹³ J travels through a 1.450 m flight tube.

The kinetic energy of the ion is given by the equation KE = mv²

where m = mass / kg

KE = kinetic energy / J

Calculate the time, in seconds, for the ion to reach the detector.

The Avogadro constant, L = 6.022 × 10²³mol⁻¹

State how the relative abundance of¹⁸⁵Re⁺ is determined in a TOF mass spectrometer.

This question is about Period 3 elements and their compounds.

Which is not a correct statement about magnesium hydroxide?

Tick (✓) one box.

Give an equation for the reaction of aluminium oxide with sulfuric acid.

Identify a reagent or test that could be used to distinguish between aqueous solutions of sulfur dioxide and sulfur trioxide with the same concentrations.

State the observation in each case.

Observation with sulfur dioxide solution

Observation with sulfur trioxide solution

The mass spectrum of the element phosphorus has a peak at = 124

Give the formula of the species responsible for this peak.

Give an equation for the reaction of phosphorus(V) oxide with sodium hydroxide solution.

Draw the displayed formula of the molecule formed when phosphorus(V) oxide reacts with water.

Table 4 shows the melting points of three substances.

Explain why the melting points of these substances are different.

You should refer to the structure of and bonding in each substance.

This question is about atomic structure.

Define the mass number of an atom.

Complete Table 3 to show the numbers of neutrons and electrons in the species

A sample of titanium contains four isotopes,⁴⁶Ti,⁴⁷Ti,⁴⁸Ti and⁴⁹Ti This sample has a relative atomic mass of 47.8 In this sample the ratio of abundance of isotopes⁴⁶Ti,⁴⁷Ti and⁴⁹Ti is 2:2:1

Calculate the percentage abundance of⁴⁶Ti in this sample.

Which does not involve the absorption of ultraviolet radiation or visible light?

This question is about the isotopes of chromium.

Give the meaning of the term relative atomic mass.

A sample of chromium containing the isotopes⁵⁰Cr,⁵²Cr and⁵³Cr has a relative atomic mass of 52.1

The sample contains 86.1% of the⁵²Cr isotope.

Calculate the percentage abundance of each of the other two isotopes.

State, in terms of the numbers of fundamental particles, one similarity and one difference between atoms of⁵⁰Cr and⁵³Cr

The sample of chromium is analysed in a time of flight (TOF) mass spectrometer.

Give two reasons why it is necessary to ionise the isotopes of chromium before they can be analysed in a TOF mass spectrometer.

A⁵³Cr⁺ ion travels along a flight tube of length 1.25 m

m = mass of the ion / kg

Calculate the time, in s, for the⁵³Cr⁺ ion to travel down the flight tube to reach the detector.

Time of flight (TOF) mass spectrometry can be used to analyse large molecules such as the pentapeptide, leucine encephalin (P).

P is ionised by electrospray ionisation and its mass spectrum is shown in Figure 2.

Describe the process of electrospray ionisation.

Give an equation to represent the ionisation of P in this process.

Equation

What is the relative molecular mass of P ? Tick (✓) one box.

A molecule Q is ionised by electron impact in a TOF mass spectrometer. The Q⁺ ion has a kinetic energy of 2.09 x 10^–15 J This ion takes 1.23 x 10^–5 s to reach the detector. The length of the flight tube is 1.50 m

Calculate the relative molecular mass of Q.

KE = mv² where m = mass (kg) and v = speed (m s^–1) The Avogadro constant, L = 6.022 x 10²³ mol^–1

Relative molecular mass

This question is about s-block metals.

Give the full electron configuration for the calcium ion, Ca²⁺

Explain why the second ionisation energy of calcium is lower than the second ionisation energy of potassium.

Identify the s-block metal that has the highest first ionisation energy.

Give the formula of the hydroxide of the element in Group 2, from Mg to Ba, that is least soluble in water.

A student added 6 cm³ of 0.25 mol dm^–3 barium chloride solution to 8 cm³ of 0.15 mol dm^–3 sodium sulfate solution. The student filtered off the precipitate and collected the filtrate.

Give an ionic equation for the formation of the precipitate. Show by calculation which reagent is in excess. Calculate the total volume of the other reagent which should be used by the student so that the filtrate contains only one solute.

Total volume of other reagent

A sample of strontium has a relative atomic mass of 87.7 and consists of three

State why the isotopes of strontium have identical chemical properties. Calculate the percentage abundance of the⁸⁸Sr isotope in this sample.

Why isotopes of strontium have identical chemical properties

A time of flight (TOF) mass spectrum was obtained for a sample of barium that

Identify the ion with the longest time of flight.

A¹³⁷Ba⁺ ion travels through the flight tube of a TOF mass spectrometer with a

The Avogadro constant, L = 6.022 × 10²³ mol^–1

Calculate the length of the flight tube in metres. Give your answer to the appropriate number of significant figures.