Bond energy calculations

This question is about cracking and the products of cracking.

Alkane molecules are often cracked.

Describe the conditions needed for cracking.

Explain how cracking alkane molecules helps to meet the demand for fuels.

The products of cracking include another type of hydrocarbon called alkenes.

Give one use of alkenes.

Do not refer to the use of alkenes as fuels.

Ethene is an alkene.

Figure 11 represents the reaction of ethene with chlorine.

Figure 11

Table 2 shows some bond energy values.

Calculate the overall energy change for the reaction of ethene with chlorine.

_ Overall energy change = ________________ kJ/mol

This question is about hydrocarbons.

Hexane (C₆H₁₄) and pentane (C₅H₁₂) are hydrocarbons in the same homologous series.

Give the name of the homologous series that includes hexane and pentane.

Give the general formula of the homologous series that includes hexane and pentane.

Explain why the boiling point of hexane is higher than the boiling point of pentane.

Complete the equation for the cracking of hexane (C₆H₁₄) into ethene and one other molecule.

Methane undergoes complete combustion with oxygen.

Figure 10 represents the equation for the reaction.

Figure 10

The energy released forming the new bonds is 814 kJ/mol greater than the energy needed to break the existing bonds.

Table 4 shows some bond energy values.

Calculate value Y in Table 4.

_ Y = ____________________ kJ/mol

Hydrogen bromide decomposes to form hydrogen and bromine.

The equation for the reaction is:

The energy needed to break the existing bonds is 103 kJ/mol greater than the energy released in forming new bonds.

Table 3 shows some bond energy values.

Y is the bond energy of a H–Br bond.

Calculate Y.

_ Y = _________________ kJ/mol

Figure 12 shows part of the reaction profile when hydrogen bromide decomposes to form hydrogen and bromine.

Complete Figure 12.

You should: label the axes draw the reaction profile label the reactant and the products label the activation energy.

Hydrogen reacts with oxygen to produce water.

Figure 6 represents the equation for the reaction.

Figure 6

Table 1 shows bond energies.

Calculate the energy released during bond formation in the reaction.

Use Figure 6 and Table 1.

Energy released = __________________ kJ/mol

In the reaction to produce water, the energy needed to break bonds is less than the energy released when bonds are formed.

Which reaction profile represents this reaction?

Tick (✓) one box.

Complete the dot and cross diagram for a water molecule.

Explain why hydrogen gas (H₂) consists of molecules rather than single atoms.

This question is about bonds.

Compare the bonding in hydrogen gas (H₂) with the bonding in copper metal.

Hydrogen reacts with oxygen to produce water.

The equation for the reaction is:

The energy released in forming new bonds is 486 kJ/mol greater than the energy needed to break the existing bonds.

Table 2 shows some bond energy values.

Y is the bond energy of a H‒H bond.

Calculate Y.