Question 1:

The correct answer is B. needs energy and is an endothermic process.

Explanation:
Chemical bonds hold atoms together because energy is required to overcome the attractive forces between them.

• Bond breaking requires an input of energy (it absorbs energy from the surroundings).

• Any process that absorbs energy is called endothermic.

Why the others are wrong:

• A is incorrect because "needs energy" is correct, but absorbing energy makes it endothermic, not exothermic.

• C is incorrect because breaking bonds does not produce energy; it consumes it. (Energy is released when bonds are formed, not broken.)

• D is incorrect because "produces energy" is wrong for bond breaking, and it is not exothermic.

Quick summary to remember:

• Bond breaking → requires energy → endothermic

• Bond forming → releases energy → exothermic

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 2:

The correct answer is:

B. exothermic which means that energy is released when bonds are made.

Bond formation releases energy, making it an exothermic process.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 3:

The correct answer is:

C. absorbed from the surroundings and the enthalpy (energy) is given a positive sign.

In an endothermic reaction, energy is taken in (absorbed) from the surroundings, and the change in enthalpy (ΔH) is positive.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 4:

The correct answer is:

D. less than the energy released on forming the new bonds.

Here's why:
In an exothermic reaction, the total energy released when new bonds are formed is greater than the total energy absorbed when existing bonds are broken. The excess energy is released to the surroundings, usually as heat.

To clarify the options:

• A and C describe endothermic behavior (more energy needed to break bonds than is released when forming them).

• B compares bond-breaking energy to bond-forming energy needed, which is not the correct comparison—we compare breaking energy to energy released on formation.

So D is the correct choice.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 5:

To find the overall energy change for the reaction, you use the formula:

Overall energy change = (Energy needed to break bonds) − (Energy released when forming bonds)

From the question:

• Energy needed to break bonds (H₂ and Cl₂) = 679 kJ

• Energy released when forming bonds (2HCl) = 856 kJ

So:

Overall energy change = 679 − 856 = −177 kJ

The negative sign indicates that energy is released, meaning the reaction is exothermic.

Correct answer: B. -177

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 6:

To calculate the energy required to break all the reactant molecules into individual atoms, you need to add up the bond energies for every bond in the reactants.

The reaction is:
2H₂ + O₂ → 2H₂O

Reactants:

• 2H₂ means there are 2 molecules of H₂.
  Each H₂ has one H–H bond.
  So total H–H bonds to break = 2 × 1 = 2
  Energy for H–H = 436 kJ/mol each
  → 2 × 436 = 872 kJ

• O₂ has one O=O bond.
  Energy for O=O = 498 kJ/mol each
  → 1 × 498 = 498 kJ

Total energy required to break all reactant bonds:
872 + 498 = 1370 kJ

So the correct answer is:

C. 1370 kJ

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 7:

To calculate the energy released when bonds in the product molecules are formed, you need to add up the bond energies for every bond in the products.

The reaction is:
2H₂ + O₂ → 2H₂O

Products:

• 2H₂O means there are 2 molecules of water.

• Each H₂O molecule has 2 O–H bonds.

• So total O–H bonds formed = 2 × 2 = 4

Energy for each O–H bond = 464 kJ/mol
→ Total energy released = 4 × 464 = 1856 kJ

(Energy released is given a negative sign in overall energy change calculations, but the question simply asks for the amount released, which is 1856 kJ.)

So the correct answer is:

D. 1856 kJ

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 8:

To calculate the overall enthalpy change for the reaction, use the formula:

Overall energy change = (Energy required to break bonds in reactants) − (Energy released when forming bonds in products)

From the previous calculations:

• Energy to break reactant bonds = 1370 kJ (from question 6)

• Energy released when forming product bonds = 1856 kJ (from question 7)

So:

Overall energy change = 1370 − 1856 = −486 kJ

The negative sign indicates that energy is released, so the reaction is exothermic.

Correct answer: A. -486 kJ

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 9:

To determine the number of bonds broken and formed, look at the balanced chemical equation:

CH₄ + 2 O₂ → CO₂ + 2 H₂O

Reactants (bonds broken):

• CH₄ (methane) has 4 C–H bonds → so 4 C–H bonds broken.

• 2 O₂ means 2 molecules of O₂, each with 1 O=O bond → so 2 O=O bonds broken.

→ Bonds broken: C–H = 4, O=O = 2

Products (bonds formed):

• CO₂ has 2 C=O bonds (each CO₂ molecule is O=C=O) → so 2 C=O bonds formed.

• 2 H₂O means 2 water molecules, each with 2 O–H bonds → total 2 × 2 = 4 O–H bonds formed.

→ Bonds formed: C=O = 2, O–H = 4

This matches:

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 10:

To calculate the overall enthalpy change, use the formula:

Overall energy change = (Energy required to break bonds) − (Energy released when forming bonds)

Step 1: Energy required to break bonds in reactants

From the previous question (question 9):

• C–H bonds broken = 4
  Energy = 4 × 415 = 1660 kJ

• O=O bonds broken = 2
  Energy = 2 × 498 = 996 kJ

Total energy to break bonds = 1660 + 996 = 2656 kJ

Step 2: Energy released when forming bonds in products

From the previous question (question 9):

• C=O bonds formed = 2
  Energy = 2 × 799 = 1598 kJ

• O–H bonds formed = 4
  Energy = 4 × 464 = 1856 kJ

Total energy released = 1598 + 1856 = 3454 kJ

Step 3: Overall enthalpy change

Overall energy change = 2656 − 3454 = −798 kJ

The negative sign indicates energy is released (exothermic reaction).

Correct answer: C. –798 kJ

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.