Honors Unit 12 Review

When new chemical bonds form, energy ____________.

• is taken into the system.

• is released from the system.

• stays the same in the system.

When the solids Ba(OH)₂ and NH₄SCN are mixed, a solution is produced and the temperature drops. Which statement about the energetics of this reaction is correct?

• The reaction is endothermic and ΔH is negative

• The reaction is endothermic and ΔH is positive

• The reaction is exothermic and ΔH is negative

• The reaction is exothermic and ΔH is positive

Based upon the graph above, what type of reaction is this?

• Endothermic

• Exothermic

Which of the following represents an exothermic reaction?

• 
• 

The following equation shows the formation of magnesium oxide from magnesium metal. Which statement is correct for this reaction?

2Mg(s) + O₂(g) → 2MgO(s) ΔH = -1204 kJ

• 1204 kJ of energy are released for every mole of magnesium reacted

• 602 kJ of energy are absorbed for every mole of magnesium oxide formed

• 602 kJ of energy are released for every mole of oxygen reacted

• 1204 kJ of energy are released for every two moles of magnesium oxide formed

For the reaction 2H₂(g) + O₂(g) → 2H₂O(g) the bond enthalpies (in kJ/mol) are

H-H = x, O=O = y, O-H = z

Which calculation will give the value, in kJ/mol, of ΔH for the reaction?

• 2x + y - 2z

• 4z - 2x - y

• 2x + y - 4z

• 2z - 2x - y

Which is an example of an endothermic physical reaction? 

• a) Ice melting 
• b) Combustion 
• c) Steam condensing 
• d) Photosynthesis

Using the table of average bond energies below the image, the ΔH for the reaction in kJ is.....

• + 160 kJ

• -63 kJ

• - 160 kJ

• -217 kJ

What is the symbol for Specific Heat

• Q
• t
• m
• C

What is the equation to measure change in Thermal Energy?

• Q=mc∆t
• Q=mc
• Q= ∆mct
• m=QC