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poizon [28]
3 years ago
12

For double-helix formation, DG can be measured to be 2 54 kJ mol 1 ( 2 13 kcal mol 1 ) at pH 7.0 in 1 M NaCl at 25 8C (298 K). T

he heat released indicates an enthalpy change of 2 251 kJ mol 1 ( 2 60 kcal mol 1 ). For this process, calculate the entropy change for the system and the entropy change for the surroundings.
Chemistry
1 answer:
levacccp [35]3 years ago
8 0

Answer:

ΔS = -661.0J/mol is the entropy change for the system

ΔS = -842J/mol.K is the entropy change for the surroundings

Explanation:

From the relationship between ΔG, T, ΔH and ΔS,

Mathematically, ΔG = ΔH - TΔS

TΔS = ΔH - ΔS

ΔS = ΔH - ΔS / T

but ΔG = -54 kJ/mol, ΔH = -251 kJ/mol and T = 25 °C (298 K)

plugging into the equation,

ΔS = -251 kJ/mol - ( -54 kJ/mol) / 298

ΔS  = -0.6610KJ/mol or in J.mol

ΔS = -661.0J/mol is the entropy change for the system

  • For entropy change for the surroundings = ΔS = ΔH/T
  • ΔS  = -251 kJ/mol / 298K
  • ΔS = -0.84KJ/mol.K or -842J/mol.K is the entropy change for the surroundings
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nadezda [96]

Answer : The oxidation-reduction reactions are:

I. reaction of a metal with a nonmetal

II. synthesis

III. combustion

Explanation :

Redox reaction or Oxidation-reduction reaction : It is defined as the reaction in which the oxidation and reduction reaction takes place simultaneously.

Oxidation reaction : It is defined as the reaction in which a substance looses its electrons. In this, oxidation state of an element increases. Or we can say that in oxidation, the loss of electrons takes place.

Reduction reaction : It is defined as the reaction in which a substance gains electrons. In this, oxidation state of an element decreases. Or we can say that in reduction, the gain of electrons takes place.

I. Reaction of a metal with a nonmetal :

When sodium react with chlorine gas then it react to give sodium chloride.

2Na+Cl_2\rightarrow 2NaCl

In this reaction, the oxidation state of sodium changes from (0) to (+1) and shows oxidation and the oxidation state of chlorine changes from (0) to (-1) and shows reduction. So, It is an oxidation-reduction reaction.

II. Synthesis reaction :

A chemical reaction where multiple substances or reactants combine to form a single product.

When hydrogen react with oxygen then it react to give water.

2H_2+O_2\rightarrow 2H_2O

In this reaction, the oxidation state of hydrogen changes from (0) to (+1) and shows oxidation and the oxidation state of oxygen changes from (0) to (-2) and shows reduction. So, It is an oxidation-reduction reaction.

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