facility.waseley.networcs.net · web viewnh3 c. ch. 3 cooh d. chf3 ... the complex rhodium ion...

Waseley Hills High School

Q1.Silicon dioxide (SiO2) has a crystal structure similar to diamond.

(a) Give the name of the type of crystal structure shown by silicon dioxide.

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(b) Suggest why silicon dioxide does not conduct electricity when molten.

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(c) Silicon dioxide reacts with hydrofluoric acid (HF) to produce hexafluorosilicic acid (H2SiF6) and one other substance.

Write an equation for this reaction.

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(Total 3 marks)

Q2.(a) Ammonia gas readily condenses to form a liquid when cooled.

(i) Name the strongest attractive force between two ammonia molecules.

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(ii) Draw a diagram to show how two ammonia molecules interact with each other in the liquid phase.Include all partial charges and all lone pairs of electrons in your diagram.


(3)

(b) Ammonia reacts with boron trichloride to form a molecule with the following structure.

State how the bond between ammonia and boron trichloride is formed.

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(c) The following table shows the electronegativity values of some elements.

H Li B C O F

Electronegativity 2.1 1.0 2.0 2.5 3.5 4.0

(i) Give the meaning of the term electronegativity.

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(ii) Suggest the formula of an ionic compound that is formed by the chemical combination of two different elements from the table.

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(iii) Suggest the formula of the compound that has the least polar bond and is formed by chemical combination of two of the elements from the table.


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(Total 9 marks)

Q3. The table below shows the electronegativity values of some elements.

H C N O

Electronegativity 2.1 2.5 3.0 3.5

(a) State the meaning of the term electronegativity.

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(b) State the strongest type of intermolecular force in the following compounds.

Methane (CH4) .............................................................................................

Ammonia (NH3) ............................................................................................(2)

(c) Use the values in the table to explain how the strongest type of intermolecular force arises between two molecules of ammonia.

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(d) Phosphorus is in the same group of the Periodic Table as nitrogen.A molecule of PH3 reacts with an H+ ion to form a PH4

+ ion.Name the type of bond formed when PH3 reacts with H+ and explain how this bond is


formed.

Type of bond ...............................................................................................

Explanation ..................................................................................................

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(e) Arsenic is in the same group as nitrogen. It forms the compound AsH3

Draw the shape of an AsH3 molecule, including any lone pairs of electrons. Name the shape made by its atoms.

Shape

Name of shape ............................................................................................(2)

(f) The boiling point of AsH3 is –62.5 °C and the boiling point of NH3 is –33.0 °C.Suggest why the boiling point of AsH3 is lower than that of NH3

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(g) Balance the following equation which shows how AsH3 can be made.

...... AsCl3 + ...... NaBH4 → ...... AsH3 + ...... NaCl + ...... BCl3

(1)(Total 14 marks)


Q4.(a) Write an equation, including state symbols, for the reaction with enthalpy change equal to the standard enthalpy of formation for CF4(g).

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(b) Explain why CF4 has a bond angle of 109.5°.

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(c) Table 1 gives some values of standard enthalpies of formation (ΔfHϴ).

Table 1

Substance F2(g) CF4(g) HF(g)

ΔfHϴ / kJ mol−1 0 −680 −269

The enthalpy change for the following reaction is −2889 kJ mol−1.

C2H6(g) + 7F2(g) 2CF4(g) + 6HF(g)

Use this value and the standard enthalpies of formation in Table 1 to calculate the standard enthalpy of formation of C2H6(g).

Standard enthalpy of formation of C2H6(g) = .................... kJ mol−1

(3)


(d) Methane reacts violently with fluorine according to the following equation.

CH4(g) + 4F2(g) CF4(g) + 4HF(g) ΔH = −1904 kJ mol−1

Some mean bond enthalpies are given in Table 2.

Table 2

Bond C−H C−F H−F

Mean bond enthalpy / kJ mol−1

412 484 562

A student suggested that one reason for the high reactivity of fluorine is a weak F−F bond.

Is the student correct? Justify your answer with a calculation using these data.

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(Total 10 marks)

Q5. Fluorine forms many compounds that contain covalent bonds.

(a) (i) State the meaning of the term covalent bond.

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(ii) Write an equation to show the formation of one molecule of ClF3 from chlorine and fluorine molecules.

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(b) Draw the shape of a dichlorodifluoromethane molecule (CCl2F2) and the shape of a chlorine trifluoride molecule (ClF3). Include any lone pairs of electrons that influence the shape.

Shape of CCl2F2 Shape of ClF3

(2)

(c) Suggest the strongest type of intermolecular force between CCl2F2 molecules.

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(d) BF3 is a covalent molecule that reacts with an F– ion to form a BF4– ion.

(i) Name the type of bond formed when a molecule of BF3 reacts with an F– ion. Explain how this bond is formed.

Type of bond .......................................................................................

Explanation .........................................................................................

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(ii) State the bond angle in the BF4– ion

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(e) An ultrasound imaging agent has the formula C4F10

It can be made by the reaction of butane and fluorine as shown in the following equation.

C4H10 + 10F2 → C4F10 + 10HF


Calculate the percentage atom economy for the formation of C4F10 in this reaction.Give your answer to three significant figures.

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(Total 11 marks)

Q6.(a) Nickel is a metal with a high melting point.

(i) State the block in the Periodic Table that contains nickel.

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(ii) Explain, in terms of its structure and bonding, why nickel has a high melting point.

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(iii) Draw a labelled diagram to show the arrangement of particles in a crystal of nickel.In your answer, include at least six particles of each type.

(2)


(iv) Explain why nickel is ductile (can be stretched into wires).

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(b) Nickel forms the compound nickel(II) chloride (NiCl2).

(i) Give the full electron configuration of the Ni2+ ion.

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(ii) Balance the following equation to show how anhydrous nickel(II) chloride can be obtained from the hydrated salt using SOCl2

Identify one substance that could react with both gaseous products.

......NiCl2.6H2O(s) + ...... SOCl2(g) ......NiCl2(s) + ......SO2(g) + ......HCl(g)

Substance ..............................................................................................(2)

(Total 9 marks)

Q7.Thallium is in Group 3 of the Periodic Table.Thallium reacts with halogens to form many compounds and ions.

(a) Draw the shape of the TlBr32– ion and the shape of the TlCl4

3– ion.Include any lone pairs of electrons that influence the shapes.

Name the shape made by the atoms in TlBr32– and suggest a value for the bond

angle.

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(4)

(b) Thallium(I) bromide (TlBr) is a crystalline solid with a melting point of 480 °C.

Suggest the type of bonding present in thallium(I) bromide and state why the melting point is high.

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(c) Write an equation to show the formation of thallium(I) bromide from its elements.

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(Total 8 marks)

Q8.The following table shows the electronegativity values of the elements from lithium to fluorine.

Li Be B C N O F

Electronegativity 1.0 1.5 2.0 2.5 3.0 3.5 4.0

(a) (i) State the meaning of the term electronegativity.

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(ii) Suggest why the electronegativity of the elements increases from lithium to fluorine.

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(2)

(b) State the type of bonding in lithium fluoride.Explain why a lot of energy is needed to melt a sample of solid lithium fluoride.

Bonding .........................................................................................................

Explanation ....................................................................................................

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(c) Deduce why the bonding in nitrogen oxide is covalent rather than ionic.

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(d) Oxygen forms several different compounds with fluorine.

(i) Suggest the type of crystal shown by OF2

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(1)

(ii) Write an equation to show how OF2 reacts with steam to form oxygen and hydrogen fluoride.

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(iii) One of these compounds of oxygen and fluorine has a relative molecular mass of 70.0 and contains 54.3% by mass of fluorine.

Calculate the empirical formula and the molecular formula of this compound.Show your working.

Empirical formula .................................................................................

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Molecular formula .................................................................................

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(Total 14 marks)

Q9.Fluorine forms compounds with many other elements.

(a) Fluorine reacts with bromine to form liquid bromine trifluoride (BrF3).State the type of bond between Br and F in BrF3 and state how this bond is formed.

Type of bond ..................................................................................................

How bond is formed ......................................................................................

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(b) Two molecules of BrF3 react to form ions as shown by the following equation.


2BrF3 BrF2+ + BrF4

–

(i) Draw the shape of BrF3 and predict its bond angle.Include any lone pairs of electrons that influence the shape.

Shape of BrF3

Bond angle ............................................................................................(2)

(ii) Draw the shape of BrF4– and predict its bond angle.

Include any lone pairs of electrons that influence the shape.

Shape of BrF4–

Bond angle ............................................................................................(2)

(c) BrF4– ions are also formed when potassium fluoride dissolves in liquid BrF3 to form

KBrF4

Explain, in terms of bonding, why KBrF4 has a high melting point.

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(d) Fluorine reacts with hydrogen to form hydrogen fluoride (HF).

(i) State the strongest type of intermolecular force between hydrogen fluoride molecules.

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(ii) Draw a diagram to show how two molecules of hydrogen fluoride are attracted to each other by the type of intermolecular force that you stated in part (d)(i). Include all partial charges and all lone pairs of electrons in your diagram.

(3)

(e) The boiling points of fluorine and hydrogen fluoride are –188 °C and 19.5 °C respectively.Explain, in terms of bonding, why the boiling point of fluorine is very low.

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(Total 15 marks)

Q10.In 2009 a new material called graphane was discovered. The diagram shows part of a model of the structure of graphane. Each carbon atom is bonded to three other carbon atoms and to one hydrogen atom.


(a) Deduce the type of crystal structure shown by graphane.

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(b) State how two carbon atoms form a carbon–carbon bond in graphane.

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(c) Suggest why graphane does not conduct electricity.

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(d) Deduce the empirical formula of graphane.

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(Total 4 marks)


Q11.Fritz Haber, a German chemist, first manufactured ammonia in 1909.Ammonia is very soluble in water.

(a) State the strongest type of intermolecular force between one molecule of ammonia and one molecule of water.

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(b) Draw a diagram to show how one molecule of ammonia is attracted to one molecule of water. Include all partial charges and all lone pairs of electrons in your diagram.

(3)

(c) Phosphine (PH3) has a structure similar to ammonia.

In terms of intermolecular forces, suggest the main reason why phosphine is almost insoluble in water.

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(Total 5 marks)


Q12.Which of these species has a trigonal planar structure?

A PH3

B BCl3

C H3O+

D CH3−

(Total 1 mark)

Q13.Which compound has the highest boiling point?

A C2H4

B C2H6

C CH3NH2

D CH3F (Total 1 mark)

Q14.Use your understanding of intermolecular forces to predict which of these compounds has the highest boiling point.

A HF

B HCl

C HBr

D HI

(Total 1 mark)

Q15.Which of these substances does not show hydrogen bonding?


A HF

B NH3

C CH3COOH

D CHF3

(Total 1 mark)

Q16.Which of these atoms has the highest electronegativity?

A Na

B Mg

C Cl

D Ar

(Total 1 mark)

Q17.(a) Explain how the electron pair repulsion theory can be used to deduce the shape of, and the bond angle in, PF3

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(b) State the full electron configuration of a cobalt(II) ion.

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(c) Suggest one reason why electron pair repulsion theory cannot be used to predict the shape of the [CoCl4]2− ion.

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(d) Predict the shape of, and the bond angle in, the complex rhodium ion [RhCl4]2−.

Shape ............................................................................................................

Bond angle .....................................................................................................(2)

(Total 10 marks)

Q18.What is the formula of calcium nitrate(V)?

A CaNO3

B Ca(NO3)2

C Ca2NO2

D Ca(NO2)2

(Total 1 mark)

Q19.Which of these substances has permanent dipole-dipole attractions between molecules?

A CCl4


B C2F4

C (CH3)2CO

D CO2

(Total 1 mark)

Q20.Which type of bond is formed between N and B when a molecule of NH3 reacts with a molecule of BF3?

A Ionic.

B Covalent.

C Co-ordinate.

D Van der Waals.

(Total 1 mark)

facility.waseley.networcs.net · web viewnh3 c. ch. 3 cooh d. chf3 ... the complex rhodium ion...

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