How many hydrogen atoms are in water?

What can be said about an endothermic reaction with a negative entropy change? View Available Hint(s) The reaction is What can b

REY [17]

Answer: The reaction is spontaneous at low temperatures

Explanation:

Let's first remember the definition of certain terms;

Enthalpy (H) in thermodynamics is defined as the heat content of a reaction. While Entropy (S) in thermodynamics is termed as the quantification of disorder or randomness of a reaction.

Gibb’s free energy change helps to determine the direction of the reaction.

Using the Gibbs free energy equation to solve this question.

∆G = ∆H - T∆S

Where;

∆G = Gibbs free energy

∆H = change in enthalpy

T= temperature of the reaction

∆S = change in entropy.

The question states that it is an exothermic reaction with negative entropy. This means that the change in both enthalpy and entropy will be negative. That is;

∆H = >0 ( it's positive)

∆S = < 0 (negative)

Let's remember that an exothermic reaction generally releases energy to it surroundings. This energy is usually released in the form of heat. Therefore, the change in enthalpy H of an exothermic reaction will always be negative. A negative change in entropy S indicates that there is a decrease in disorder, with respect to the reaction.

Using Gibb’s free energy equation at constant temperature and pressure, we have;

∆G = ∆H - T∆S

Now, the change in enthalpy and change in entropy can be written as follows;

∆H = >0 ( it's positive)

∆S = < 0 (negative)

Substitute these values in the above equation;

∆G = ∆H - T - (∆S)

∆G = ∆H + T∆S

According to the sign convention seen in the equation above,

Change in ∆G will be negative <0 when the value ∆H is greater than T∆S.

This change can occur only at low temperatures. Thus, this reaction is spontaneous at low temperatures.

5 0

3 years ago

In each reaction box place the best reagent and conditions from the list below benzene 3 boxes

den301095 [7]

Answer : The correct answer is 1) AlCl₃ - CH₃Cl 2) HNO₃ -H₂SO₄ at room temperature 3) Fuming HNO₃ -H₂SO₄ at 90-100 ⁰ C heat .

I think this reaction is forming 2,4,6- trinitrotoluene from benzene, since the product is not mentioned. Following are the steps to convert Benzene to 2,4,6 trinitrotoluene .

Step 1: Conversion of Benzene to Toluene .

Benzene can be converted to toluene by Friedel Craft Alkylation of benzene . In this reaction reagent AlCl₃ and Ch3Cl is used . Electrophile CH³⁺ is produced which attached on carbon of benzene and formation of Toluene and HCl occur.

$Benzene \frac{AlCl3}{Ch3Cl}> Toulene + HCl$

Step 2 : Conversion of Toluene to dinitrotoluene.

Dinitritoluene is prepared from toluene by Nitration . This reaction uses Electrophilic substitution mechanism . The reagents used are HNO₃ and H₂SO₄ at room temperature . These reagents produces NO₂⁺ ( nitronium ion ), a electrophile which attacks on C2 and C4 Carbon atoms of Toluene.

Toluene $Tolune \frac{HNO3 -H2SO4}{30-40 degree C} -> 2,4- dinitrotoluene$

Step 3) Conversion of Dinitro toluene to trinitrotoluene.

This reaction is extended nitration of toluene . Further nitration is done in extreme condition . The temperature of reaction is increased to 90- 100 ⁰ C . Due to which there is more production of NO²⁺ ion occurs from HNO₃ -H₂SO₄ and they attack on C6 carbon atom of dinitrotoluene which forms 2,4,6- trinitrotoluene.

Dinitrotoluene $2,4 -dinitrotoluene \frac{fuming HNO3-H2So4}{90-100 C} -> 2,4,6-trinitrotoluene.$

So over all reaction uses three reagents in order :

$Benzene \frac{AlCl3}{CH3Cl} -> Toluene \frac{HNO3-H2So4}{room temp} -> 2,4-dinitrotoluene \frac{Fuming HNO3 -H2SO4}{Heating at 90-100 C} -> 2,4,6-trinitrotoluene .$