cylamorgan1
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Part A

Choose the thermochemical equation that illustrates [tex]$\Delta H _{ f }$[/tex] for [tex]$Li _2 SO _4$[/tex].

A. [tex]$2 Li ^{+}( aq )+ SO _4{ }^{2-}( aq ) \rightarrow Li _2 SO _4( aq )$[/tex]

B. [tex][tex]$16 Li ( s )+ S _8(s$[/tex], rhombic $)+16 O _2(g) \rightarrow 8 Li _2 SO _4(s)$[/tex]

C. [tex][tex]$2 Li ( s )+1 / 8 S_8(s,$[/tex] rhombic $)+2 O _2(g) \rightarrow Li _2 SO _4(s)$[/tex]

D. [tex]$Li _2 SO _4( aq ) \rightarrow 2 Li ^{+}( aq )+ SO _4{ }^{2-}( aq )$[/tex]

E. [tex][tex]$8 Li _2 SO _4(s) \rightarrow 16 Li ( s )+ S _8(s$[/tex], rhombic $)+16 O _2(g)$[/tex]

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Sagot :

GinnyAnswer
To choose the thermochemical equation that illustrates the formation enthalpy ([tex]\( \Delta H_f \)[/tex]) for [tex]\( \text{Li}_2\text{SO}_4 \)[/tex], we need to identify the equation that represents the formation of 1 mole of [tex]\( \text{Li}_2\text{SO}_4 \)[/tex] from its elements in their standard states.

Let's examine each option:

1. [tex]\( 2 \text{Li}^+(aq) + \text{SO}_4^{2-}(aq) \rightarrow \text{Li}_2\text{SO}_4(aq) \)[/tex]

This equation represents the formation of [tex]\( \text{Li}_2\text{SO}_4 \)[/tex] in the aqueous phase from ions, not from elements in their standard states.

2. [tex]\( 16 \text{Li}(s) + \text{S}_8(s,\text{rhombic}) + 16 \text{O}_2(g) \rightarrow 8 \text{Li}_2\text{SO}_4(s) \)[/tex]

This equation involves the formation of 8 moles of [tex]\( \text{Li}_2\text{SO}_4 \)[/tex] from elements in their standard states, but we need the formation of exactly 1 mole. We'll need to divide everything by 8 for it to properly show the formation of 1 mole, so this is close but not a perfect match.

3. [tex]\( 2 \text{Li}(s) + \frac{1}{8} \text{S}_8(s,\text{rhombic}) + 2 \text{O}_2(g) \rightarrow \text{Li}_2\text{SO}_4(s) \)[/tex]

This accurately shows 1 mole of [tex]\( \text{Li}_2\text{SO}_4 \)[/tex] being formed from its elements in their standard states (solid lithium, solid sulfur, and gaseous oxygen). This satisfies the requirement for [tex]\( \Delta H_f \)[/tex].

4. [tex]\( \text{Li}_2\text{SO}_4(aq) \rightarrow 2 \text{Li}^+(aq) + \text{SO}_4^{2-}(aq) \)[/tex]

This equation represents the dissociation, not the formation, of [tex]\( \text{Li}_2\text{SO}_4 \)[/tex].

5. [tex]\( 8 \text{Li}_2\text{SO}_4(s) \rightarrow 16 \text{Li}(s) + \text{S}_8(s,\text{rhombic}) + 16 \text{O}_2(g) \)[/tex]

This equation is the reverse of the formation reaction and deals with the breakdown of [tex]\( \text{Li}_2\text{SO}_4 \)[/tex], not its formation.

Hence, the correct thermochemical equation that illustrates the formation enthalpy ([tex]\( \Delta H_f \)[/tex]) for [tex]\( \text{Li}_2\text{SO}_4 \)[/tex] is:
[tex]\[ 2 \text{Li}(s) + \frac{1}{8} \text{S}_8(s,\text{rhombic}) + 2 \text{O}_2(g) \rightarrow \text{Li}_2\text{SO}_4(s) \][/tex]

And thus, the correct answer is:
[tex]\[ Option\ 3 \][/tex]

So, the correct choice is:
[tex]\[ 3 \][/tex]
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