OL U4 Zone 3

What do thermochemical equations show?

• The amount of reactants used in the reaction.

• The amount of products formed during the reaction.

• How much heat is absorbed or released during the reaction.

• The speed at which the reaction occurs.

What does the symbol 'l' represent in a chemical equation?

• Liquid state of a substance.

• Solid state of a substance.

• Gas state of a substance.

• Aqueous state of a substance.

What is the state of carbon in the reaction C(s) + 2S(s) → CS₂(l)?

• Solid.

• Liquid.

• Gas.

• Plasma.

What is an exothermic reaction?

• A reaction that absorbs energy in the form of heat.

• A reaction that releases energy in the form of heat.

• A reaction that occurs at a constant temperature.

• A reaction that requires a catalyst to proceed.

What is an endothermic reaction?

• A reaction that releases energy into its surroundings.

• A reaction that absorbs energy from its surroundings.

• A reaction that occurs at a constant temperature.

• A reaction that produces heat.

What does the symbol 'g' represent in a chemical equation?

• Gaseous state of a substance.

• Gravitational force acting on a substance.

• Ground state of an atom.

• Gasoline as a fuel source.

What is the standard enthalpy of formation (ΔH°f)?

• The change in enthalpy when one mole of a compound is formed from its elements in their standard states.

• The total energy change during a chemical reaction at constant pressure.

• The energy required to break one mole of bonds in a compound.

• The heat absorbed or released during a phase change of a substance.

What does ΔH mean?

• Entropy

• Enthalpy

• Energy

• Temperature

What is the formula for calculating heat (q) absorbed or released?

• q = mcΔT

• q = mΔT/c

• q = mcT

• q = mTΔC

What type of reaction is characterized by energy being absorbed?

• Exothermic

• Endothermic

• Catalytic

• Combustion