11.2 Lesson: Standard Heat of Formation

Drag and Drop

Standard condition is ​

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degrees Celsius and ​

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​atmosphere.

Drag these tiles and drop them in the correct blank above

25

1

0

760

Open Ended

What is the Standard Heat of Formation or $$\Delta H_f^o$$ ?

​Formula for Solving Heat of Formation Problems

​Example:

​What is the total heat of formation for the products?

3(0 kJ) + 2(-74.8 kJ) = -149.6 kJ

What is the total heat of formation for the reactants?

4(-214.8 kJ)+ 2(-110.5 kJ) = -1080.2 kJ

​What is the net results?

ΔH = products - reactants

ΔH = -149.6 kJ - (-1080.2 kJ) = 930.6 kJ

Multiple Choice

Is the enthalpy for the last problem endothermic or exothermic?

• endothermic because the result is positive

• endothermic because the result is negative

• exothermic because the result is negative

• exothermic because the result is postive

​Number of positive means endothermic (energy going into)

Number is negative means exothermic ( energy is going out)

Math Response

Try this. Calculate the Enthalpy using heat of formation for the reaction shown.

Type answer here

Correct Answer: 256

Deg^°

Rad

Multiple Choice

Is the enthalpy for the last problem endothermic or exothermic?

• endothermic because the result is positive

• endothermic because the result is negative

• exothermic because the result is negative

• exothermic because the result is postive

Math Response

One more. Calculate the enthalpy using the heat of formation.

Type answer here

Correct Answer: -189

Deg^°

Rad

Multiple Choice

Is the enthalpy for the last problem endothermic or exothermic?

• endothermic because the result is positive

• endothermic because the result is negative

• exothermic because the result is negative

• exothermic because the result is postive