What are the formal charges on the sulfur (s), carbon (c), and nitrogen (n) atoms, respectively, in the resonance structure that
contributes most to the stability of the thiocyanate ion, scn−?
2 answers:
Answer:
Sulfur: -1
Carbon: 0
Nitrogen: 0
Explanation:
The thiocyanate ion SCN- can have only two resonance structures, which are:
S - C ≡ N <--------> S = C = N
In the first structure, we have one single bond and one triple bond, in this case, the negative charge is located in the sulfur. This is because Sulfur have 6 electrons and those electrons are present in the atom, (see picture below), and counting the electron that is sharing with the Carbon, the total electrons that sulfur has is 7 (It has one more than usual). Carbon and nitrogen are already stable with 0 of formal charge, because carbon can only have 4 electrons which 1 is sharing with sulfur and the other 3 with the nitrogen, and nitrogen have 5 electrons, three sharing with carbon and the other two kept it for itself.
In the second structure, the negative charge of the sulfur is transfered to the nitrogen, meaning that it has 6 electrons the nitrogen (formal charge -1) and carbon and sulfur with 4 and 6 electrons respectively.
Between these two structures, the most stable is the first one basically because Sulfur is a better nucleophile than the Nitrogen, and can form stronger hydrogen bond in acid, giving more stable structure.
Answer:
0, 0, -1
Explanation:
There are three resonance contributors to the resonance hybrid of the SCN⁻ ion.
The one on the right is the least stable because it has the greatest separation of charge.
The remaining structures each have one negative charge.
The structure in the middle is the most stable and most important contributor because it has the negative charge on the most electronegative atom — N.
The formal charges on S, C, and N are 0, 0, and -1.
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Given that, an experiment to measure the enthalpy change for the reaction of aqueous copper(II) sulfate, CuSO4(aq) and zinc, Zn(s) was carried out in a coffee cup calorimeter; the heat of the reaction in the whole system is calculated to be 2218.34 kJ
Heat of reaction (i.e enthalpy of reaction) is the quantity of heat that is required to be added or removed when a chemical reaction is taken place in order to maintain all of the compounds present at the same temperature.
The formula used to calculate the heat of the reaction can be expressed as follows:
Q = mcΔT
where:
- Q = quantity of heat transfer
- m = mass
- c = specific heat of water = 4.18 kJ/g °C (constant)
- ΔT = change in temparature
From the information given:
- The initial temperature (T₁) = 25° C
- The final temperature (T₂) = 91.5° C
∴
The change in temperature i.e. ΔT = T₂ - T₁
ΔT = 91.5° C - 25° C
ΔT = 66.5° C
The number of moles of CuSO₄ = 1.00 mol/dm³ × 50.0 cm³
= 0.05 moles
- Since the molar mass of CuSO₄ = 159.609 g/mol
Then;
Using the relation:
By crossing multiplying;
mass of CuSO₄ = number of moles of CuSO₄ × molar mass of CuSO₄
mass of CuSO₄ = 0.05 moles × 159.609 g/moles
mass of CuSO₄ = 7.9805 grams
∴
Using the formula from above:
Q = mcΔT
Q = 7.9805 g × 4.18 kJ/g °C × 66.5° C
Q = 2218.34 kJ
Therefore, we can conclude that the heat of the reaction is 2218.34 kJ
Learn more about the chemical reaction here: