Why is ∆H negative in an exothermic reaction? from Chemistry

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 Multiple Choice QuestionsShort Answer Type

51.

Define heat capacity ?

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52.

What is the realtionship between Cand Cv?

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53.

What are exothermic and endothermic reactions?

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54.

What is the standard state of the substance?

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55. Why is ∆H negative in an exothermic reaction?


Exothermic reactions are accompanied by the evolution of heat. It means that enthalpy of the reactants is more than the enthalpy of the products i.e.
                   Hr > Hp

But           


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56. Why ∆H is positive in an endothermic reaction?
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57.

State with reason whether the work is done by the system on the surroundings or on the system by the surroundings if the following change occurs at constant pressure:
Sn left parenthesis straight s right parenthesis space plus space 2 Cl subscript 2 left parenthesis straight g right parenthesis space rightwards arrow space space SnCl subscript 4 left parenthesis straight s right parenthesis

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58.

What is the enthalpy of formation of the most stable form of an element in its standard state?

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59. The thermochemical equation for the formation of water is:
2 straight H subscript 2 left parenthesis straight g right parenthesis space plus space straight O subscript 2 left parenthesis straight g right parenthesis space space rightwards arrow space space 2 straight H subscript 2 straight O left parenthesis straight I right parenthesis space increment subscript straight r straight H to the power of 0 space equals space minus 571.8 space kJ

What is the standard enthalpy of formation of water?
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60.

Comment on the thermodynamic stability of NO(g), given

 


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