Take this Quiz: A-Level Chemistry: Energetics | Zestly

Question 1

The standard enthalpy change of formation for liquid ethanol (C2H5OH) is -277 kJ/mol. Which of the following equations correctly represents this definition?

Accepted Answer

2C(s) + 3H2(g) + 0.5O2(g) ->C2H5OH(l)

Question 2

Which of the following statements correctly describe the sign conventions for enthalpy changes in chemical reactions?

Accepted Answer

Exothermic reactions have a negative $\Delta H$ value.

Question 3

Which of the following factors contribute to the difference between experimental enthalpy values obtained from simple calorimetry and theoretical (data book) values?

Accepted Answer

Heat loss to the surroundings.

Question 4

Calculate the enthalpy change for the reaction H2 + Cl2 ->2HCl using the following mean bond enthalpies: H-H = 436 kJ/mol, Cl-Cl = 242 kJ/mol, H-Cl = 431 kJ/mol.

Answer

-184 kJ/mol

Answer

-368 kJ/mol

Answer

+184 kJ/mol

Answer

+368 kJ/mol

Question 5

The standard enthalpy of neutralisation is defined as the enthalpy change when one mole of water is formed from the reaction of an acid and a base. Which of the following is true regarding this value?

Answer

It is always positive.

Answer

It is approximately -57 kJ/mol for strong acids and strong bases.

Answer

It involves the reaction of H+ ions with OH- ions.

Answer

It depends on the specific acid and base used, even for strong ones.