What do I need to know in order to be able to do this question?
1. Answer the following questions related to manganese compounds.
(a) Manganese has several common oxidation states.
(i) Write the complete electron configuration for an Mn atom in the ground state.
(ii) When manganese forms cations, electrons are lost from which subshell first? Identify both the number
and letter associated with the subshell.
A student performs an experiment to produce a manganese salt of unknown composition, MnxCly(aq), and
determine its empirical formula. The student places a sample of Mn(s) in a beaker containing excess HCl(aq), as
represented by the following equation.
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5
y
x Mn(s) + y HCl(aq) → MnxCly(aq) + H ( 2 g)
The student heats the resulting mixture until only MnxCly(s) remains in the beaker. The data are given in the
following table.
Mass of empty beaker 60.169 g
Mass of beaker and Mn(s) 61.262 g
Mass of beaker and Mn Cl after heating to constant mass x y 62.673 g
(b) Calculate the mass of Cl in the sample of MnxCly(s) remaining in the beaker.
(c) Calculate the number of moles of Cl in the sample of MnxCly(s) remaining in the beaker.
(d) The student determines that 0.0199 mol of Mn was used in the experiment. Use the data to determine the
empirical formula of the Mn Cl (s) x y .
(e) The student repeats the experiment using the same amounts of Mn and HCl and notices that some of the
MnxCly splatters out of the beaker as it is heated to dryness. Will the number of moles of Cl calculated for
this trial be greater than, less than, or equal to the number calculated in part (c) ? Justify your answer.
(f) Another compound of manganese, MnO2, is used in alkaline batteries, represented by the following diagram.
Some half-reactions are given in the table.
(i) Based on the half-reactions given in the table, write the balanced net ionic equation for the reaction that
has the greatest thermodynamic favorability.
(ii) Calculate the value of  Ecell for the overall reaction.
(iii) Calculate the value of ΔG° in kJ/molrxn.
(iv) A student claims that the total mass of an alkaline battery decreases as the battery operates because the
anode loses mass. Do you agree with the student’s claim? Justify your answer.

Answer:
(a) (i) For the correct answer:
Accept one of the following:
• 22 62 62 5 12233 43 sspspsd
• 2 5 [Ar] 4 3 s d
1 point
 (ii) For the correct answer, consistent with part (a)(i):
4s
1 point
Total for part (a) 2 points
(b) For the correct calculated value:
62.673 g 61.262 g 1.411 g Cl − =
1 point
(c) For the correct calculated value, consistent with part (b):
1 mol Cl 1.411 g Cl 0.03980 mol Cl 35.45 g Cl × =
1 point
(d) For the correct answer, consistent with part (c):
2
0.03980 mol Cl 2 mol Cl MnCl 0.0199 mol Mn 1 mol Mn = ⇒
1 point
(e) For the correct answer and a valid justification:
Less than. If some of the mass of aqueous Mn Cl x y is lost due to splattering, the final mass
of the dry beaker and Mn Cl x y will be decreased, which will decrease the calculated mass
and number of moles of chlorine in the dry solid.
1 point
(f) (i) For the correct balanced equation:
2 2 2 3
2
2 2 3
2 MnO ( ) H O( ) 2 Mn O ( ) 2 OH ( )
 Zn( ) 2 OH ( ) ZnO( ) H O( ) 2
 2 MnO ( ) Zn( ) Mn O ( ) ZnO( )
s l e s aq
s aq s l e
ss s s
− −
− −
+ +→ +
+ →++
+→ +
1 point
(ii) For the correct calculated value, consistent with part (f)(i):
Ecell = −− 0.15 V ( 1.28 V) = 1.43 V 
1 point
(iii) For the correct calculated value, consistent with part (f)(ii):
2 mol 96,485 C 1.43 J 1 kJ 276 kJ/mol 1 mol 1 mol 1 C 1000 J rxn rxn
e G nFE
e
−
− ∆ °=− °=− × × × =−
1 point
(iv) For the correct answer and a valid justification:
Accept one of the following:
• Disagree. The battery is enclosed, so no change in the total mass will occur.
• Disagree. All reactants and products are in the solid phase, so the mass of the
sealed battery will remain the same (no gases enter or exit the battery).
1 point
Total for part (f) 4 points
Total for question 1 10 points