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4

The enthalpy of the elements in their standard states is taken as zero. So the enthalpy of formation of a compound may be

A. negative

B. positive

C. zero

D. negative or positive

Correct Answer :

D. negative or positive


Related Questions

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4

The apparatus used for measuring the heat changes is known as ...

A. Thermometer

B. Ammeter

C. Voltameter

D. Calorimeter

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4

The heat of neutralisation of a strong acid and a strong base is equal to......................K.Cal gm eq-1

A. 27.3

B. 31.7

C. 15.7

D. 13.7

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4

In a spontaneous irreversible process, the total entropy of the system & its surroundings

A. is constant

B. decreases

C. increases

D. is zero

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4

A person requires 2870 Kcal of energy for leading a normal life. If heat of combustion of cane sugar is -1349 Kcal then he must consume...................kg of cane sugar daily.

A. 728   

B. 448

C. 142

D. 224

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4

The heat change taking place in the reaction
H2 OIH2Og,HfH2 Og=-57K CalHfH2 OI=68.3K Calis..?

A. -11.3 Kcal

B. +11.3 Kcal

C. -17.3 Kcal

D. 125.5 Kcal

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4

10 gm of ice at 0°C is placed into 100 gm of water at 50°C. Hie temperature of water after the whole ice has melted will be

A. 32.8°C

B. 19.5°C

C. 31.8°C

D. 38.1°C

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4

A person requires 2870 Kcal of energy for leading a normal life. If heat of combustion of cane sugar is -1349 Kcal then he must consume...................kg of cane sugar daily.

A. 728

B. 448

C. 142

D. 224

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4

The molar entropy of vaporisation of a liquid at its boiling point is

A. 25 JK-1mole-1

B. 100 JK-1mole-1

C. 80 JK-1mole-1

D. 90 JK-1mole-1

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4

Heat of neutralisation of HCI and NaOH is -57.32 KJ per gram equivalent and that of acetic acid and NaOH is -55.23 KJ per gram equivalent. The heat of dissociation of acetic acid per gram equivalent should be?

A. -2.09

B. 2.09

C. -2.1%

D. 2.196

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4

The highest temperature at which vapour pressure of a liquid can be measured is..

A. the boiling point of the liquid

B. critical solution temperature

C. ionisation temperature

D. inversion temperature

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4

The factor that does not influence the heat of reaction is...

A. method by which reactants change to products

B. chemical state of the reactants and products

C. whether it is taking place at constant temperature

D. All the above

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4

For the reaction
C+O2CO2        H1=394 KJ mole-12CO+O22CO2H2=569 KJH for 1 mole formation of CO is...?

A. +265.0 KJ mole-1

B. -165.0 KJ mole-1

C. -109.5 KJ mole-1

D. +109.5 KJ mole-1

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4

The solution energy of AI+++ion is more than that of Mg+++ due to...

A. high ionisation energy of AI+++ ion

B. greater size of AI+++ ion

C. greater charge on AI+++ ion

D. small size of AI+++ ion

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4

The total heat content of a system is known as....

A. Enthalpy

B. Thermal Energy

C. Entropy

D. Activation Energy

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4

Heat of Reaction between sodium hydroxide and hydrochloric acid is 57.32 KJ mole-1. So heat of dissociation of water is

A. -57.32 KJ mole-1

B. +23.7KJ mole-1

C. +57.32 KJ mole-1

D. -13.7KJ mole-1

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4

The enthalpy of the elements in their standard states is taken as zero. So the enthalpy of formation of a compound may be

A. negative

B. positive

C. zero

D. negative or positive

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4

Heat of reaction

A. depends on the rate of reaction

B. depends on pressure

C. is independent of temperature

D. may or may not depend on temperature

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4

Internal energy of the elements is assigned a value of................................cal per mole at standard states.

A. 5

B. 9

C. 99

D. 0

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4

Heat of fusion of a molecular solid is

A. high

B. low

C. average

D. very high

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4


In a thermal decomposition reaction, sign of H may be...

A. positive   

B. negative

C. No sign

D. positive or negative.

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4

For a reaction 2 SO2g+O2g2 SO3;gG°=-141.8 KJ-1
So the driving force for the reaction is?

A. +198.0 KJ

B. -198 KJ

C. -118.67 KJ

D.  187.8 KJ

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4

In reaction Cs+O2gCO2g H=-94.3 K cal mol-1

A. HP < HR

B. HP > HR

C. 2HP = 3HR

D. HP = HR

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4

On burning hydrogen in an atmosphere of chlorine, 1.65 gm of HC1 was obtained and 1 Kcal of heat was liberated. The heat of formation of HC1 should be ?

A. -21.12 Kcal mol-1

B. -44.2 Kcal mol-1

C. 500 cal mol-1

D. 500 cal gm-1

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4

Heat of combustion of S (Rhombic) and S (monoclinic) are -297.5 KJ and -300 KJ mole-1 respectively. So the heat of transformation of SR to SM is

A. 2.5 KJ mole-1

B. +1.5 KJ mole-1

C. +297.5

D. 3.5 KJ mole-1

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4

Heat of combustion of methane and ethane are -291.7 Kcal & — 441.2 Kcal respectively:

A. Methane is a better fuel because ethane is poisonous

B. Methane is a better fuel than C2H6

C. Ethane is a better fuel than CH4

D. Both are equally efficient as a fuel

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4

35.5 gm of chlorine gas is allowed to expand freely in vacuum at 25°C. Then AH for this process is

A. Zero

B. 25 cal.

C. 17.2 J

D. 52.4 cal

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4

If temperature is kept constant during the reaction, the process is said to be.......................

A. Adiabatic

B. Isobaric

C. Isothermal

D. none of above

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4

1 Joule is equal to

A. 2.39 Cal

B. 0.04184 Cal

C. 1.390 Cal

D. 0.239 Cal