A student conducting a calorimetry investigation determines a negative ∆H. What does the negative value indicate about the react
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Answer:
Explanation:
4NH₃ (g) + 3O₂ (g) ⇒ 2N₂ (g) + 6H₂ O(1)
Δ
ΔH r =(2ΔH f(N 2 )+6ΔH f (H 2 O(l)))−(4ΔH f (NH 3 (g))+3ΔH f (O 2 (g)))
ΔH rex =[2×0+6×(−286)]−[4×(−46)+3×0]=−1716+186
ΔH rex =−1532kJ/mol
Thermodynamics is a branch of physical chemistry that studies heat and its effects and interactions. Governed by the four main laws, thermodynamics plays a huge role in physics and chemistry, and is also responsible for the law of conservation of energy, a fundamental rule in science.
The coefficients of the hydrocarbon and water is 61 and it is explained below.
Explanation:
We have to balance the chemical equation that describes the combustion of octane C₈H₁₈. The combustion of octane involves burning this hydrocarbon in the presence of excess oxygen,O 2. Because octane is a hydrocarbon, that is the compound that contains only carbon and hydrogen, the reaction will produce two products carbon dioxide CO 2 and water H 2 O.
The unbalanced chemical equation is
C₈H₁₈ + O₂ → CO₂ + H₂O
To balance this equation, we have 8 present on the reactant side, so multiply the carbon dioxide by 8 to get 8 atoms of carbon on the products side.
C₈H₁₈ + O₂ → 8 CO₂ + H₂O
Now, we have 18 on the reactant side and 2 on the products side, so multiply the water molecule by 9 to get
C₈H₁₈ + O₂ → 8 CO₂ + 9 H₂O
8 * 2 atoms O + 9 *1 atoms O = 25 atoms O
By adding fractional coefficient to O₂ we get
C₈H₁₈ + O₂ → 8 CO₂ + 9 H₂O
Multiply all the coefficients by 2 we get,
2C₈H₁₈ + ( * 2) O₂ → 8 * 2 CO₂ + 9* 2 H₂O
The balance equation is
2C₈H₁₈ + 25 O₂ → 16 CO₂ + 18 H₂O
Add the coefficients to get their sum
= 2 +25 + 16 +18 = 61
Thus, The coefficients of the hydrocarbon and water is 61