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The heat of formation is the change in e...

The heat of formation is the change in enthalpy accompanying the formation of a substance from its elements at 298 K and 1 atm pressure. Since the enthalpies of elements are taken to be zero, the heat of formation `(DeltaH)` of compounds

A

Is always negative

B

Is always positive

C

May be negative or positive

D

Is zero

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The correct Answer is:
C
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ERRORLESS -THERMODYNAMICS AND THERMOCHEMISTRY -ORDINARY THINKING (Objective Questions) Heat of reaction
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  2. An exothermic reaction is one in which the reacting substances :

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  3. The heat of formation is the change in enthalpy accompanying the forma...

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  4. When 50 cm^(3) of a strong acid is added to of an alkali, the temperat...

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  5. H(2)(g)+(1)/(2)O(2)(g)rarrH(2)O(l), DeltaH " at "298 K=-285.8 kJ ...

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  6. If, H(2)(g)+Cl(2)(g)rarr 2HCl(g) , Delta H^(@)=-44 Kcal 2Na(s)+2HCl...

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  7. In order to decompose 9 grams of water 142.5 KJ heat is required. Henc...

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  8. Compounds with high heat of formation are less stable because

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  9. The enthalpy of combustion of methane at 25^(@)C is 890 kJ. The heat l...

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  10. The enthalpy of the reaction H(2)(g)+(1)/(2)O(2)(g)toH(2)O(g) is Del...

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  11. The enthalpy of formation of ammonia is -46.0 KJ mol^(-1) . The entha...

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  12. 8 gm of CH(4) is completely burnt in air. The number of moles of water...

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  13. If ( I ) C + O 2 → C O 2 , Q 1 ( I I ) C + 1 2 O 2 → C O , Q 2 ( ...

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  14. Given: i. 2Fe(s) +(3)/(2)O(2)(g) rarr Fe(2)O(3)(s), DeltaH^(Theta) =...

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  15. The standard heats of formation of CH(4), H(2)O and CH(3)OH are -76, ...

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  16. During the melting of solid, which of the following is true

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  17. The energy released on combustion of 1 mole of C((s)) with gaseous oxy...

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  18. For an exothermic reaction, which is true

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  19. The enthalpy of neutralization of oxalic acid by strong acid is - 25.4...

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  20. Which of these species has a standard enthalpy of formation equal to z...

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