A Thermochemistry Knowledge Quiz

The heat of combustion of a substance is always negative because combustion is an exothermic process. During combustion, a substance reacts with oxygen to produce heat, light, and often other products. Since heat is released during this reaction, the heat of combustion is negative.

The Born Haber cycle is a method used to calculate the lattice energy of ionic solids. This energy is the amount of energy released when gaseous ions come together to form a solid crystal lattice. The cycle involves a series of steps, including the formation of gaseous ions, the formation of an ionic solid from these ions, and the calculation of the lattice energy based on the enthalpy changes in these steps. Therefore, the Born Haber cycle is specifically used for determining the lattice energies of ionic solids.

Work done is not a state function of a system because it depends on the path taken to reach a particular state, rather than just the initial and final states. State functions only depend on the current state of the system and are independent of the process or path taken to reach that state. In contrast, work done is a path function as it is influenced by factors such as the distance traveled, applied force, and the nature of the process.

Enthalpy is the correct answer because it refers to the total heat content of a system. It includes both the internal energy of the system and the energy required to displace the environment's pressure. Enthalpy is a state function, meaning it only depends on the current state of the system and not the path taken to reach that state.

One calorie is equivalent to 4.18 joules. This means that if you have 1 calorie of energy, it is equal to 4.18 joules of energy.

A bomb calorimeter is used in constant volume calorimetry because it allows for the measurement of the heat released or absorbed during a chemical reaction that occurs at constant volume. This type of calorimetry is particularly useful for reactions that involve gases, as it prevents any change in volume and ensures that all heat energy is accounted for. By measuring the temperature change in the bomb calorimeter, the heat of the reaction can be determined.

The system in this scenario is the oxygen. The balloon and the freezer are both components of the system, but the oxygen is the substance that is being focused on. The question asks to identify the system, and since the oxygen is the main element being discussed, it is the correct answer.

The enthalpy of formation of CO2 can be determined by subtracting the enthalpy of combustion of C from the enthalpy of formation of CO2. Since the enthalpy of combustion of C is -393.5 kJ mole-1, the enthalpy of formation of CO2 would also be -393.5 kJ mole-1.

To write the thermochemical equation for the enthalpy of combustion of an element, we need to consider the following factors:
a. 1 mole of the element as a reactant, as combustion involves the reaction of the element with oxygen.
c. Standard enthalpy values of all the substances involved, as thermochemical equations are typically written with standard enthalpy values.
d. A balanced equation of 1 mole of the element, as the equation needs to be balanced to accurately represent the reaction.

The given question is asking for the value of q (heat) when ∆V (change in volume), P (pressure), and ∆E (change in energy) are all equal to zero. The correct answer is "None of these" because the question does not provide enough information to determine the value of q. The question only specifies the conditions for ∆V, P, and ∆E, but does not mention any specific value or relationship for q. Therefore, without further information, it is not possible to determine the value of q.

All substances have a standard enthalpy of formation, which is the change in enthalpy when one mole of the substance is formed from its elements in their standard states. Therefore, none of the substances listed (O2, H2O, ZnO) have a zero value for their standard enthalpy of formation.

The correct answer is "the complete ionization of acids and bases." This is because strong acids and strong bases completely dissociate into ions when they are dissolved in water. As a result, the reaction between them during neutralization is complete and all of the acid and base molecules are converted into ions. This leads to the formation of water and a salt, resulting in the same enthalpy of neutralization for all strong acids and strong bases.