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Enthalpy 2 (Worksheets)

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Work in groups on these problems. You should try to answer the questions without referring to your textbook. If you get stuck, try asking another group for help.

Q1

Calculate the \(\Delta{H^o_{rxn}}\) from the \(\Delta{H^o_f}\)  for the following reaction:

  1. \[PbO_{(s)}   +   CO(g)     \rightarrow    Pb(s)     +   CO_2 (g)\]
  2. \[ SiH_{4 \,(g)}   +  2 O_2 (g)    \rightarrow    SiO_2 (s)   +  2 H_2O (l)\]
  3. \[2 FeS_{2\, (s)}  +  5.5 O_2 (g)    \rightarrow  Fe_2O_3 (s)  +  4 SO_2 (g)\]

 

 
\(\Delta{H^o_f}\)  kJ/mol
 
\(\Delta{H^o_f}\)  kJ/mol
\(CO_{(g)}\)
-110.5
\(Pb_{(s)}\)
0
\(CO_{2\,(g)}\)
-393.5
\(PbO_{(s)}\)
-217.3
\(Fe_2O_{3\,(s)}\)
-824.2
\(SiH_{4\,(g)}\)
34.3
\(FeS_{2\,(s)}\)
-177.5
\(SiO_{2\,(s)}\)
-910.9
\(H_2O_{(l)}\)
-285.8
\(SO_{2\,(g)}\)
-296.8
\(O_{2\,(g)}\)
0
   

Q2

Determine the \(\Delta{H^o_{rxn}}\)  using Hess's Law

a)  Determine the enthalpy of formation for \(MnO_{2\,(s)}\)

\[Mn_{(s)} + O_{2\,(g)} \rightarrow MnO_{2\,(s)}\]

Given:

\[4Al_{(s)} + 3O_{2\,(g)} \rightarrow 2Al_2O_{3\,(s)}\]

with \(\Delta H\)   = -3352 kJ/mol

\[4Al_{(s)} + 3MnO_{2\,(s)} \rightarrow 3Mn_{(s)} + 2Al_2O_{3\,(s)}\]

with \(\Delta H\) = -1937 kJ/mol

 

b)  Determine the heat of hydrogenation for

\[C_3H_{4\,(g)} + 2H_{2\,(g)} \rightarrow C_3H_{8\,(g)}\]

Given:

\[2H_{2\,(g)} + O_{2\,(g)} \rightarrow 2H_2O_{2\,(l)}\]

with \(\Delta H\)  = -571.6 kJ/mol

\[C_3H_{4\,(g)} + 4O_{2\,(g)} \rightarrow 3CO_{2\,(g)} + 2H_2O_{(l)}\]

with \(\Delta H\)  = -1937 kJ/mol

\[C_3H_{8\,(g)} + 5O_{2\,(g)} \rightarrow 3CO_{2\,(g)}  + 4H_2O{(l)}\]

with \(\Delta H\) = -2220 kJ/mol