IB Chemsl Intro To Energetics

1. Which statement about the given reaction is correct?

The volume increases and the reaction is endothermic.

A solid is produced and the reaction is exothermic.

A solution is produced and the reaction is endothermic.

A solution is produced and the reaction is exothermic.

The correct answer is "A solid is produced and the reaction is exothermic." This means that during the reaction, a solid substance is formed, and the reaction releases heat. The formation of a solid indicates a precipitation reaction, where two or more substances combine to form a solid product. The release of heat indicates an exothermic reaction, where energy is released in the form of heat.

Explanation

The correct answer is "A solid is produced and the reaction is exothermic." This means that during the reaction, a solid substance is formed, and the reaction releases heat. The formation of a solid indicates a precipitation reaction, where two or more substances combine to form a solid product. The release of heat indicates an exothermic reaction, where energy is released in the form of heat.

2. When solid potassium chloride is added to water, the temperature of the liquid goes down. Which conclusion can be made from this observation?

The process is exothermic.

The process is endothermic.

Very little potassium chloride dissolves in water.

All solids dissolve with a temperature decrease.

When solid potassium chloride is added to water and the temperature of the liquid goes down, it indicates that the process is endothermic. This means that energy is absorbed from the surroundings, causing a decrease in temperature.

Explanation

When solid potassium chloride is added to water and the temperature of the liquid goes down, it indicates that the process is endothermic. This means that energy is absorbed from the surroundings, causing a decrease in temperature.

3. When steam is passed through white-hot coke, a reaction occurs and the temperature of the coke falls.What does this indicate?

Coke contains impurities

The reaction is exothermic

Coke is an oxidising agent

The reaction is endothermic

The given answer suggests that the reaction between steam and white-hot coke is endothermic. This means that the reaction requires or absorbs heat from its surroundings, causing the temperature of the coke to decrease.

Explanation

The given answer suggests that the reaction between steam and white-hot coke is endothermic. This means that the reaction requires or absorbs heat from its surroundings, causing the temperature of the coke to decrease.

4. The equations for three changes are given below: Which of the following changes are endothermic?

Reaction 1 only

Reactions 1 and 3 only

Reactions 1 and 2 only

Reactions 2 and 3 only

The given answer states that reactions 1 and 2 are the only endothermic changes. This means that these two reactions require an input of energy in order to occur. Reactions 1 and 3, as well as reactions 2 and 3, are not endothermic changes because they do not require an input of energy.

Explanation

The given answer states that reactions 1 and 2 are the only endothermic changes. This means that these two reactions require an input of energy in order to occur. Reactions 1 and 3, as well as reactions 2 and 3, are not endothermic changes because they do not require an input of energy.

5. Which of the following statements DOES NOT describe the enthalpy level diagram found below:

The reaction is endothermic.

Energy is absorbed by the system.

The total energy change for bond formation is greater than that for bond breaking.

The product possesses more energy than the reactants.

The enthalpy level diagram shows the energy changes that occur during a chemical reaction. It represents the energy of the reactants and products. The diagram indicates whether the reaction is endothermic or exothermic, and in this case, it shows that the reaction is endothermic because energy is absorbed by the system. It also shows that the product possesses more energy than the reactants. However, the statement that the total energy change for bond formation is greater than that for bond breaking is incorrect. The diagram actually shows that the energy change for bond breaking is greater than that for bond formation.

Explanation

The enthalpy level diagram shows the energy changes that occur during a chemical reaction. It represents the energy of the reactants and products. The diagram indicates whether the reaction is endothermic or exothermic, and in this case, it shows that the reaction is endothermic because energy is absorbed by the system. It also shows that the product possesses more energy than the reactants. However, the statement that the total energy change for bond formation is greater than that for bond breaking is incorrect. The diagram actually shows that the energy change for bond breaking is greater than that for bond formation.

6. Which process is BEST represented by the energy level diagram found below:

Adding ammonium thiocyanate to barium hydroxide

Melting of mercury metal

Sublimation of dry ice

Neutralization of acid and base

The energy level diagram represents the process of neutralization of acid and base. This process involves the reaction between an acid and a base to form a salt and water. The energy level diagram shows the initial energy of the reactants, the activation energy required for the reaction to occur, and the final energy of the products. In neutralization, the energy of the reactants is higher than the energy of the products, indicating an exothermic reaction where energy is released.

Explanation

The energy level diagram represents the process of neutralization of acid and base. This process involves the reaction between an acid and a base to form a salt and water. The energy level diagram shows the initial energy of the reactants, the activation energy required for the reaction to occur, and the final energy of the products. In neutralization, the energy of the reactants is higher than the energy of the products, indicating an exothermic reaction where energy is released.

7. A student was asked to write down five pieces of information that could be obtained from the equation below: Which one of the following pieces of information is INCORRECT?

Magnesium chloride is soluble in water

Total energy of the products is greater than that of the reactants

One mole of magnesium produces one mole of hydrogen molecules

Total energy of the products is less than that of the reactants

The equation mentioned in the question is likely a chemical equation representing a reaction. According to the law of conservation of energy, the total energy of the products should be equal to the total energy of the reactants. Therefore, the statement "total energy of the products is greater than that of the reactants" is incorrect.

Explanation

The equation mentioned in the question is likely a chemical equation representing a reaction. According to the law of conservation of energy, the total energy of the products should be equal to the total energy of the reactants. Therefore, the statement "total energy of the products is greater than that of the reactants" is incorrect.

8. Which of the following statements regarding the reaction below is NOT correct? Heat of reaction is also given.

The energy of the reactants is less than that of the product.

For each mole of the solid product formed in the reaction, 10.2 kJ of heat is released.

The energy involved in bond forming is greater than that of bond breaking.

If the reaction is carried out in an insulated container, the temperature in the container would increase.

The statement "The energy of the reactants is less than that of the product" is incorrect because according to the law of conservation of energy, energy cannot be created or destroyed in a chemical reaction. The total energy of the reactants must be equal to the total energy of the products.

Explanation

The statement "The energy of the reactants is less than that of the product" is incorrect because according to the law of conservation of energy, energy cannot be created or destroyed in a chemical reaction. The total energy of the reactants must be equal to the total energy of the products.

9. The dissolving of potassium iodide in water is an endothermic process. Which graph shows the temperature changes that occur when potassium iodide is stirred with water until no further change in temperature is observed?

A

B

C

D

Graph B shows the temperature changes that occur when potassium iodide is stirred with water until no further change in temperature is observed. This is because an endothermic process absorbs heat from its surroundings, causing a decrease in temperature. In Graph B, the temperature initially decreases as the potassium iodide dissolves in water, and eventually levels off when no further change in temperature is observed.

Explanation

Graph B shows the temperature changes that occur when potassium iodide is stirred with water until no further change in temperature is observed. This is because an endothermic process absorbs heat from its surroundings, causing a decrease in temperature. In Graph B, the temperature initially decreases as the potassium iodide dissolves in water, and eventually levels off when no further change in temperature is observed.

10. The formation of hydrogen iodide from hydrogen and iodine is an endothermic reaction. H-H + I-I→ H-I + H-I What may be deduced from this information?

The total energy change in bond formation is less than that of bond breaking.

The products possess less energy than the reactants.

The formation of H-I bonds absorbs energy.

The number of bonds broken is greater than the number of bonds formed.

From the given information, it can be deduced that the formation of hydrogen iodide from hydrogen and iodine is an endothermic reaction. This means that energy is absorbed during the formation of H-I bonds. Since the reaction is endothermic, the total energy change in bond formation is less than that of bond breaking, indicating that more energy is required to break the existing bonds in the reactants than is released during the formation of the new bonds in the product.

Explanation

From the given information, it can be deduced that the formation of hydrogen iodide from hydrogen and iodine is an endothermic reaction. This means that energy is absorbed during the formation of H-I bonds. Since the reaction is endothermic, the total energy change in bond formation is less than that of bond breaking, indicating that more energy is required to break the existing bonds in the reactants than is released during the formation of the new bonds in the product.