(a)
Write the balanced half-reactions for the overall process:
Oxidation: Se^2- (aq) → Se
(s) + 2e-
Reduction: 2So3^2- (aq) + 3H2O (l) + 4e- →
S2O3^2- + 6OH- (aq)
(b)
Assuming E sulfite is 0.57 V, compute E selenium:
E anode = E cathode – E cell
= -0.57 – 0.35
=
-.092
From the provided data, the unknown mixture was composed of salt, salicylic acid, and sand. It is understandable that the student suspected the presence of sand, yet scientific experimentation must verify such assumptions. The test involving salt and salicylic acid reveals that salt dissolves in water, while salicylic acid is only slightly soluble, and sand does not dissolve at all. By introducing the unknown into water, the salt would dissolve first, followed by the partial dissolution of salicylic acid. Heating the mixture could allow for the evaporation of salicylic acid, resulting in the remaining salt. If traces of sand were observed in the dissolved sample, it could suggest contamination.
Answer:
The enthalpy of the second intermediate equation is altered by halving its value and changing the sign.
Explanation:
Let's examine both the first and second intermediate reactions alongside the overall equation concerning the examined process;
First reaction;
Ca (s) + CO₂ (g) + ½O₂ (g) → CaCO₃ (s) ΔH₁ = -812.8 kJ
Second reaction;
2Ca (s) + O₂ (g) → 2CaO (s) ΔH₂ = -1269 kJ
Thus, the overall reaction becomes;
CaO (s) + CO₂ (g) → CaCO₃ (s) ΔH =?
According to Hess's law, which states that the total heat change in a reaction is equal to the sum of the heat changes for each step, we cannot simply sum the enthalpies for this overall reaction. Instead, we obtain the overall enthalpy by halving the second intermediate reaction's enthalpy and changing its sign before adding, as illustrated below;
Enthalpy of Intermediate reaction 1 + ½(-Enthalpy of Intermediate reaction 2) = Enthalpy of Overall reaction
False, it's solely heterogeneous. Explanation: The degradation of the ozone layer caused by CFC molecules happens in the gaseous state since it does not involve liquids or solids at stratospheric conditions. Additionally, the reaction occurs independently as ozone is chemically unstable, eliminating the need for a catalyst.
Let's represent molecules with symbols as follows:
C₂O₄ = X
and
H₂O = Y
Then,
K [ Co (X)₂ (Y)₂ ]
Since Potassium (K) has an oxidation number of +1
To achieve neutrality, the oxidation number of the coordination sphere needs to equal -1.
Thus,
[ Co (X)₂ (Y)₂ ] = -1
Given that,
the O.N of X is -2
Therefore,
O.N of (X)₂ equals -4
Additionally,
O.N of H₂O is zero since it remains neutral. Therefore,
[Co - 4 + 0 ] = -1
Or,
Co = -1 + 4
Co = +3
Conclusion:
The oxidation number for the coordination sphere is -1, and the oxidation state of copper is +3.
