Hess's Law and Enthalpy Diagram

Using the equations below:

C_(s) + O_2(g) → CO_2(g) ∆H = –390 kJ

Mn_(s) + O_2(g) → MnO_2(s) ∆H = –520 kJ

what is ∆H (in kJ) for the following reaction?

MnO_2(s) + C_(s) → Mn_(s) + CO_2(g)

• 910

• 130

• -130

• -910

Tags

NGSS.HS-PS1-4

Which of the following statements are true for the reaction:

SO_2(g) + ¹/₂O_2(g) ↔ SO_3(g) ΔH = –92 kJ mol^-1

Where ↔ indicates that the reaction can proceed in the forward and the reverse direction.

• The forward and reverse reaction both produce 92 kJ of energy.

• This is an endothermic reaction.

• The reverse reaction has an enthalpy of +92 kJ mol^-1.

• Collecting the SO3 produced in the liquid state would not change the measured enthalpy.

Tags

NGSS.HS-PS1-4

A chemical reaction that requires energy is a

• exothermic reaction 
• endothermic reaction 
• over reaction 
• redox reaction

Tags

NGSS.HS-PS1-4

The standard enthalpy change of formation values of two oxides of phosphorus are:

P_4(s) + 3O_2(g) → P₄O_6(s) ΔH_f = –1600 kJ mol^–1

P_4(s) + 5O_2(g) → P₄O_10(s) ΔH_f = –3000 kJ mol^–1

What is the enthalpy change, in kJ mol^–1, for the reaction below?

P₄O_6(s) + 2O_2(g) → P₄O_10(s)

• +4600

• +1400

• –1400

• –4600

When iron nails get rusty, heat is released.  What process is this?

• Exothermic
• Endothermic

Tags

NGSS.HS-PS1-4

ΔH value in an endothermic reaction is a positive number.

• True
• False

During an endothermic reaction in a beaker if we are part of the surroundings and touched the beaker, it would feel _______. 

• Warm
• Cold

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-4

In an endothermic reaction the products have 

• more energy than the reactants
• less energy than the reactants
• the same energy as the reactants
• no energy

Tags

NGSS.HS-PS1-4

In an exothermic reaction the products have

• more energy than the reactants
• the same energy as the reactants
• less energy than the reactants
• no energy

Tags

NGSS.HS-PS1-4

What units are used to measure energy?

• Watts
• Newtons
• Joules
• kilowatts