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svp [43]
2 years ago
9

For a particular reaction, ΔH∘=67.7 kJ/molΔH∘=67.7 kJ/mol and Δ????∘=126.9 J/(mol⋅K).ΔS∘=126.9 J/(mol⋅K). Assuming these values

change very little with temperature, at what temperature does the reaction change from nonspontaneous to spontaneous in the forward direction?
Chemistry
1 answer:
Pavlova-9 [17]2 years ago
8 0

Answer:

T=533.49\, K

For temperatures higher than 533.49 K we will see a spontaneous reaction, and for temperatures lower than that the reaction will not be spontaneous.

Explanation:

When are chemical reactions spontaneous? To find out we need to look at the reaction's change in Gibbs Free energy:

\Delta G=\Delta H-T\Delta S

When this is greater than zero, the reaction isn't spontaneous, when it is less than zero, we have a spontaneous reaction. The reaction must then change from spontaneous to non spontaneous when \Delta G=0. If we insert that into our equation we get:

0=\Delta H-T\Delta S\\\\T=\frac{\Delta H}{\Delta S}

That is the temperature at which the reaction's spontaneity will change, plugging in our values we find:

T=533.49\, K

At that temperature we have  \Delta G=0.

Now, at a temperature greater than this one, the entropy term in our equation for the Gibbs' free energy of reaction will take over, and make  \Delta G, thus the reaction will be spontaneous.

On the other hand, if we lower the temperature, we will have a smaller entropy term, and we will have:  \Delta G>0. That is, the reaction will not be spontaneous. Therefore for temperatures higher than 533.49 K we will see a spontaneous reaction, and for temperatures lower than that the reaction will not be spontaneous.

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Which of the following statements are True about the experimental process used in the Diels Alder reaction?
vovikov84 [41]

Here we have to get the correct statements among the given, applicable for Diels-Alder reaction.

The true statements in case Diels-Alder reaction are-

1. An excess of Maleic anhydride is used.

2. The I.R. of the products are indistinguishable.

The Diels-Alder reaction is the most is the most important cyclo-addition reaction in organic chemistry. These are addition reactions in which ring systems are formed without eliminating any compounds.

There remains one diene and one dienophile. The reaction is reversible in nature and requires elevated temperature to obtain its transition state. The reaction rate become faster in certain condition like using of polar solvents.

Among the given statements the following statements are true-

1. An excess of maleic anhydride (the most effective di-enophile) is used to process the reaction in forward direction.

2. The products obtain in this reaction are stereoisomers thus are indistinguishable by infrared spectroscopy (IR).

The statements which are not true for the Diels-Alder reaction:

3. The re-crystallization of the products by any polar solvent like methanol is not feasible as it will cause the retro reaction due to stability of the transition state in polar solvent.

4. Cleaning of glassware are compulsory for any reaction it is not specifically true for Diels-Alder reaction.

5. The reaction occurs at elevated temperature thus flame is required.

 

8 0
2 years ago
The empirical formula of a gaseous fluorocarbon is CF2. At a certain temperature and pressure, a 1-L volume holds 8.93 g of this
dimaraw [331]

Answer:

C₄F₈

Explanation:

Using their mole ratio to compute their mass

molar mass of carbon = 12.0107 g/mol

molar mass of fluorine gas = 37.99681

let x = mass of carbon

given mass of fluorine = 1.70 g

x / 12.01067 = 1.70 / 37.99687

cross multiply

x = ( 1.70 × 12) / 37.99687 = 20.4 / 37.99687 = 0.53688 g

mass of one mole of CF₂ = 0.53688 + 1.70 = 2.23688 g

number of mole of CF₂ = 8.93 g / 2.23688 = 3.992 approx 4

molecular formula of CF₂ = 4 (CF₂) = C₄F₈

3 0
2 years ago
Titanium has five common isotopes: 46Ti (8.0%), 47Ti (7.8%), 48Ti (73.4%), 49Ti (5.5%), 50 Ti (5.3%). What is the average atomic
zhannawk [14.2K]
(46x8.0)+(47x7.8)+(48x73.4)+(49x5.5)+(50x5.3) = 4792.3

4792.3/100 = 47.923 this is the average atomic mass of Titanium
6 0
2 years ago
How many grams of CaF2 are present in 1.25 L of a 0.15 M solution of CaF2? How do I find the grams I am confused on that part?
dybincka [34]

Answer:

Mass = 14.64 g

Explanation:

Given data:

Volume of solution = 1.25 L

Molarity of Solution = 0.15 M

Mass of CaF₂ = ?

Solution:

Molarity is used to describe the concentration of solution. It tells how many moles are dissolve in per litter of solution.

Formula:

Molarity = number of moles of solute / L of solution

We will calculate the number of moles of CaF₂ and then determine the mass by using number of moles.

0.15 M =  number of moles of solute / 1.25 L

number of moles of solute = 0.15 M ×  1.25 L

number of moles of solute = 0.1875 mol/L × L

number of moles of solute = 0.1875 mol

Mass in gram:

Mass = number of moles × molar mass

Mass = 0.1875 mol ×78.07 g/mol

Mass = 14.64 g

7 0
2 years ago
How many moles NaOH are contained in 65.0 mL of a 2.20 M solution of NaOH in H2O?
saw5 [17]
The   number  of  moles  of  NaOh that  are    contained  in  65ml  of   2.20M  solution  NaOh  in H2o  is  calculated  using  the  below  formula


moles  =  molarity  x  volume  /1000

that  is     65 x2.20  /1000=  0.143  moles

0 0
2 years ago
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