Enthalpy

What is the sign of ΔH for an exothermic reaction?

• Positive

• Negative

• Zero

• Undefined

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

What does ΔH represent in a chemical reaction?

• The change in pressure during a reaction.

• The change in temperature of the reactants.

• The change in enthalpy during a chemical reaction, indicating whether the reaction absorbs or releases heat.

• The change in concentration of the products.

Tags

NGSS.HS-PS3-1

In the reaction C + O2 → CO2 + 60kJ, what is ΔH?

• ΔH = 60 kJ, indicating the reaction is endothermic.

• ΔH = -60 kJ, indicating the reaction is exothermic.

• ΔH = 0 kJ, indicating the reaction is at equilibrium.

• ΔH = 30 kJ, indicating the reaction is slightly exothermic.

Tags

NGSS.HS-PS3-1

What is specific heat?

• The amount of energy required to raise the temperature of 1 gram of a substance by 1°C.

• The total heat energy contained in a substance.

• The heat required to change a substance from solid to liquid at its melting point.

• The energy needed to increase the temperature of a substance without changing its state.

Tags

NGSS.HS-PS3-4

How does the enthalpy change affect reaction spontaneity?

• A negative ΔH often indicates that a reaction is spontaneous, while a positive ΔH may require additional factors to be spontaneous.

• A positive ΔH always indicates that a reaction is spontaneous.

• Enthalpy change has no effect on reaction spontaneity.

• A negative ΔH means the reaction will never be spontaneous.

What is the sign of ΔH for an endothermic reaction?

• Positive

• Negative

• Zero

• Undefined

Tags

NGSS.HS-PS1-4

What is the formula for calculating ΔH?

• ΔH = H(products) - H(reactants)

• ΔH = H(reactants) - H(products)

• ΔH = H(products) + H(reactants)

• ΔH = H(products) * H(reactants)

Tags

NGSS.HS-PS3-1

What is Enthalpy?

• A measure of the total energy of a thermodynamic system, including internal energy and the energy required to make room for it by displacing its environment.

• A measure of the temperature of a substance in a thermodynamic system.

• The energy required to change the state of a substance without changing its temperature.

• The energy released during a chemical reaction.

Tags

NGSS.HS-PS1-4

What does it mean if ΔH is zero?

• It indicates that there is no net change in enthalpy during the reaction, meaning energy is neither absorbed nor released.

• It means that the reaction is exothermic and energy is released.

• It signifies that the reaction is endothermic and energy is absorbed.

• It shows that the reaction has reached completion and no further changes will occur.

Tags

NGSS.HS-PS1-4

For the reaction 2NO + O2 → 2NO2, if ΔH = -112 kJ, what does this imply?

• The reaction absorbs 112 kJ of energy, making it endothermic.

• The reaction releases 112 kJ of energy, making it exothermic.

• The reaction has no energy change, making it isothermal.

• The reaction requires 112 kJ of energy to proceed, making it non-spontaneous.

Tags

NGSS.HS-PS1-4