Incorrect Test Answers Flashcards by Matt Miles

Describe the process of electrospray ionisation? [4 marks]

1) Dissolved in solvent.
2) Injected through a needle.
3) A high voltage is applied.
4) This causes a proton to be gained.

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State the meaning of the term periodicity. [1 mark]

Repeating patterns of physical and chemical properties.

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What is the equation for the reaction of solid sodium chloride with concentrated sulphuric acid?

What is the role of sulphuric acid?

2NaCl + H₂SO₄ —-> Na₂SO₄ + 2HCl

Proton donor.

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What reaction(s) occurs when NaF reacts with H₂SO₄?

What is observed?

NaF + H₂SO₄ —-> NaHSO₄ + HF

Misty fumes of HF gas.

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What reaction(s) occurs when NaCl reacts with H₂SO₄?

What observations are there?

NaCl + H₂SO₄ —-> NaHSO₄ + HCl

Misty fumes of HCl.

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What reaction(s) occur when NaBr reacts with H₂SO₄?

What observations are there?

NaBr + H₂SO₄ —-> NaHSO₄ + HBr

2HBr + H₂SO₄ —-> Br₂ + SO₂ + 2H₂O

Misty fumes of HBr and brown gas (Br₂).

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What reaction(s) occur when NaI reacts with H₂SO₄?

What observations are there?

NaI + H₂SO₄ —-> NaHSO₄ + HI

2HI + H₂SO₄ —-> I₂ + SO₂ + 2H₂O

6HI + SO₂ —-> H₂S + 3I₂ + 2H₂O

Fumes of H₂S and solid iodine (purple).

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What is the equation for AgBr reacting with concentrated ammonia solution?

AgBr + 2NH₃ —-> Ag(NH₃)₂⁺ + Br⁻

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What is the shape of a ClF₄⁻ ion?

Square planar.

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Explain why Mg(OH)₂ is only weakly alkaline.

It is only sparingly soluble and so less dissolves and less is therefore dissociated.

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State whether a solution containing [Fe(H₂O)₆]³⁺ ions has a higher or lower pH than a solution containing an equal concentration of [Fe(H₂O)₆]²⁺ ions and explain why. [3 marks]

A lower pH.

Fe³⁺ has a higher charge density than Fe²⁺ which means it attracts the bonding electrons more. This weakens the O-H bonds which makes it more likely to dissociate.

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How do you test for an alcohol?

React with acidified potassium dichromate with heat.

It should turn from orange to green.

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Why is fluted filter paper used?

Large surface area which allows the solution to travel quickly through the filter paper.

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What is the value of a H-O-H bond angle in water?

Explain the bond angle. [4 marks]

104.5 degrees.

There are two lone pairs and two bonding pairs of electrons. Lone pairs have a greater repulsion than bonding pairs of electrons. This causes a bent shape to be formed and the bond angle reduced from 109.5 degrees to 104.5 degrees.

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What is the purpose of a salt bridge?

Allows ions to pass freely between the two electrolytes.

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How can an electrochemical cell reaction be changed in order to go to completion?

Replace voltmeter with lamp.

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What effect does changing temperature have on Kₚ and yield?

It shifts the position of equilibrium to favour the endothermic reaction and therefore affects the yield.

It also affects the value of Kₚ.

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What effect does changing pressure have on Kₚ and yield?

It shifts the position of equilibrium to the side with the fewest number of moles and therefore affects the yield.

It does NOT affect Kₚ.

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What effect does a catalyst have on Kₚ and yield?

It neither affects the yield or value of Kₚ.

It will make the equilibrium be reached faster.

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What is the definition of empirical formula?

The simplest ratio of atoms of each element in a compound.

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What is the definition of relative molecular mass?

The average mass of a molecule on a scale where an atom of carbon-12 is exactly 12.

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What is the colour change at the end point of the titration between iron and manganate (VII) ions?

Colourless —-> Pink.

What are the reagents for a dehydration reaction?

Concentrated sulphuric acid.

A calculation of the enthalpy of lattice formation of silver iodide based on a perfect ionic model gives a smaller numerical value than the experimental value.

Explain this difference. [2 marks]

AgI contains some covalent character.

The forces holding the lattice together are stronger.

Calculate the pH of a 0.0131 mol dm⁻³ solution of calcium hydroxide at 10°C. Kw = 2.93 x 10⁻¹⁵ mol² dm⁻⁶ at 10°C. [3 marks]

12.95

State the type of crystal structure shown in sulphur trioxide. [1 mark]

Molecular

Explain why silicon dioxide has a higher melting point than sulphur trioxide. [4 marks]

Covalent bonds between atoms in SiO₂. Van der Waals forces between molecules in SO₃. Covalent bonds are stronger than van der Waals forces. Covalent bonds take more energy to be broken.

Write an equation for the reaction of sulphur trioxide with potassium hydroxide solution. [1 mark]

SO₃ + 2KOH ----> K₂SO₄ + H₂O

Solution A is [Cu(H₂O)₆]Cl₂. An excess of ammonia was added to solution A to form solution B. Write an ionic equation for the reaction that occurs. [1 marks]

[Cu(H₂O)₆]²⁺ + 4NH₃ ----> [Cu(NH₃)₄(H₂O)₂]²⁺ + 4H₂O

Solution A is [Cu(H₂O)₆]Cl₂. Reagent D was added to another sample of solution A to form a yellow-green solution. Write an ionic equation for the reaction that occurs when the yellow-green solution is formed from solution A. [1 mark]

[Cu(H₂O)₆]²⁺ + 4Cl⁻ ----> [CuCl₄]²⁻ + 6H₂O

Explain why the reaction between the aldehyde, CH₃CH₂CH₂CH₂CHO, and KCN and dilute acid forms a racemic mixture. [3 marks]

The carbonyl group is planar. Attack from either side has equal probability.

Write an equation for the reaction of concentrated nitric acid with concentrated sulphuric acid to form the species that reacts with nitrobenzene. [1 mark]

2H₂SO₄ + HNO₃ ----> NO₂⁺ + 2HSO₄⁻ + H₃O⁺

Why is an aromatic amine less basic than an aliphatic amine?

The lone pair of electrons on the nitrogen atom is delocalised into the benzene ring. Therefore, it is less available to donate or accept a H⁺ ion.

What reagents and conditions are required to convert a haloalkane into a nitrile?

Alcoholic and aqueous KCN.

What reagents are required to reduce a nitrile into an amine?

LiAlH₄ in dry ether. Or H₂ with a nickel catalyst.

Concentrated sulphuric acid reacts with solid sodium chloride. State the role of the sulphuric acid. [1 mark]

Proton donor.

Describe the method the student should use to purify the benzoic acid [6 marks]

1) Dissolve crude product in hot water of a minimum volume. 2) Filter to remove insoluble impurities. 3) Cool to recrystallise. 4) Filter under reduced pressure with Buchner apparatus. 5) Wash with cold solvent and dry.

V₂O₅ can be used as a catalyst in the Contact Process. Which is a step in the Contact Process in which the vanadium is oxidised? A) SO₂ + V₂O₅ ----> SO₃ + 2VO₂ B) SO₃ + 2VO₂ ----> SO₂ + V₂O₅ C) 2VO₂ + 1/2 O₂ ----> V₂O₅ D) V₂O₅ ----> 2VO₂ + 1/2 O₂

Explain why the enthalpy of hydration becomes less exothermic from Li⁺ to K⁺. [2 marks]

The size increases and so the charge density decreases. The electrostatic attraction between metal ion and Oδ⁻ of water decreases.

Explain, with the aid of an equation, why a solution containing [Al(H₂O)₆]³⁺ has a pH less than 7. [3 marks]

[Al(H₂O)₆]³⁺ + H₂O ⇌ [Al(H₂O)₅(OH)]²⁺ + H₃O⁺ Al³⁺ has a high charge density which weakens the OH bond in water, releasing H⁺ ions.

Solid sodium chloride reacts with concentrated sulphuric acid. State the role of the chloride ions in the reaction. [1 mark]

Base.

Give an equation for the redox reaction between solid sodium bromide and concentrated sulphuric acid. [1 mark]

2NaBr + 2H₂SO₄ → Na₂SO₄ + Br₂ + SO₂ + 2H₂O

Give two ways of maximising the yield of propanal obtained by distillation of the reaction mixture. [2 marks]

Keep the temperature to below the boiling point of the other products. Cool the distillate / reaction vessel.

Explain how stereoisomerism occurs. [1 marks]

C=C bond cannot rotate and each carbon has two different groups attached.

How does adding water to an equilibrium mixture affect the amount of products and reactants?

Adding water causes the concentrations to fall. The equilibrium moves to the side with more moles to oppose the decrease in concentration.

Suggest a value for the enthalpy of hydrogenation of cyclohexa-1,3-diene and justify your value. [3 marks]

Between -239 and -121. Double bonds separated by one single bond which allows some delocalisation/overlap of p-orbitals.

What type of compounds does thermal cracking make?

Produces lots of alkenes

What type of compounds does catalytic cracking make?

Mostly aromatic hydrocarbons and the alkanes needs to produce motor fuels

How are nitrous oxides created inside a car engine?

N₂ + O₂ => 2NO 2NO + O₂ => 2NO₂

What are the equations for how a catalytic converter works?

2NO => N₂ + O₂ | 2NO + 2CO => N₂ + 2CO₂

What two monomers is Nylon 6,6 made from?

Hexanedioic acid and 1,6-diaminohexane.

What two monomers is Kevlar made from?

Benzene-1,4-dicarboxylic acid and 1,4-diaminobenzene.

What two monomers is Terylene made from?

Benzene-1,4-dicarboxylic acid and ethane-1,2-diol.