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Q1.
Figure 1 shows the displayed formula equation for the reaction of
hydrogen sulfide with oxygen.
Figure 1
2 H – S – H + 3 O=O ….> 2 H-O-H + 2 O=S=O
The table below shows some of the bond energies
In the reaction the energy released forming new bonds is 1034 kJ/mol
greater than the energy needed to break existing bonds.
Calculate the bond energy X for the bond.
Use Figure 1 and the table above.
___________________________________________________________
X = _______________kJ/mol
(5)
-
Step 1: Calculate bonds broken
C–H bonds:
4
×
364
=
1456
4×364=1456
C–C bonds:
3
×
498
=
1494
3×498=1494
Total bonds broken =
1456
+
1494
=
2950
kJ/mol
1456+1494=2950kJ/molStep 2: Add energy change (given)
Bonds formed =
2950
+
1034
=
3984
kJ/mol
2950+1034=3984kJ/molStep 3: Set up equation for unknown bond X
Bonds formed =
4
𝑋
+
4
×
464
4X+4×464
So,
4
𝑋
+
1856
=
3984
4X+1856=3984Step 4: Rearrange to solve for X
4
𝑋
=
3984
−
1856
=
2128
4X=3984−1856=2128Step 5: Divide to find X
𝑋
=
2128
4
=
532
kJ/mol
X=
4
2128
=532kJ/mol
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