Multiple choice om kemisk energi og termodynamik

Multiple choice questions (Paper 1 type): Core - SL & HL

1.What energy changes occur when chemical bonds are formed and broken?

A.Energy is absorbed when bonds are formed and when they are broken.

B.Energy is released when bonds are formed and when they are broken.

C.Energy is absorbed when bonds are formed and released when they are broken.

D.Energy is released when bonds are formed and absorbed when they are broken.

(Total 1 mark)

2.Which statements about exothermic reactions are correct?

I.They have negative ?H values.

II.The products have a lower enthalpy than the reactants.

III.The products are more energetically stable than the reactants.

A.I and II only

B.I and III only

C.II and III only

D.I, II and III

(Total 1 mark)

3.When the solids Ba(OH)2 and NH4SCN are mixed, a solution is produced and the temperature drops.

Ba(OH)2(s) + 2NH4SCN(s) ? Ba(SCN)2(aq) + 2NH3(g) + 2H2O(l)

Which statement about the energetics of this reaction is correct?

A.The reaction is endothermic and ?H is negative.

B.The reaction is endothermic and ?H is positive.

C.The reaction is exothermic and ?H is negative.

D.The reaction is exothermic and ?H is positive.

(Total 1 mark)

4.The following equation shows the formation of magnesium oxide from magnesium metal.