Chemical energetics

Which of the following is true about the formation of bonds between molecules?

• Energy is given off when bonds are formed between molecules.

• Energy is absorbed by the molecule when bonds are formed.

• Energy is neither given off nor absorbed when bonds are formed.

Tags

NGSS.HS-PS1-4

Which of the following statement is true about the breaking of bonds between molecules?

• To break a bond between molecules, energy must be released by the molecule

• To break a bond between molecules, no energy is needed.

• To break a bond between molecules, energy must be absorbed by the molecule.

Tags

NGSS.HS-PS1-4

Which letter corresponds to the energy of the products?

• A
• B
• C
• D

Tags

NGSS.HS-PS1-4

If ∆H is negative, the reaction is?

• exothermic
• endothermic

Tags

NGSS.HS-PS1-4

ΔH value in an endothermic reaction is a positive number.

• True
• False

Tags

NGSS.HS-PS3-1

The energy level diagram for the reaction between magnesium and hydrochloric acid is shown.

• Energy is given out during the reaction

• The products are less stable than the reactants

• The reaction is endothermic.

Tags

NGSS.HS-PS1-4

Which reaction is endothermic?

• acid neutralising alkali causing a temperature increase

• adding magnesium to hydrochloric acid

• calcium carbonate decomposing when heated combustion of fossil fuels

Tags

NGSS.HS-PS1-4

In an endothermic reaction, heat is ...

• taken in or absorbed
• given out or released 

Tags

NGSS.HS-PS1-4

Is photosynthesis an exothermic or endothermic reaction?

• Endothermic
• Exothermic
• Neither

Tags

NGSS.HS-PS1-4

NGSS.HS-LS1-5

The initial temperature was measured to be 20^oC and the final temperature was 10^oC. The reaction was

• exothermic

• endothermic

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-4