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ryzh [129]
3 years ago
12

When does the composition of a substance does not change?

Chemistry
1 answer:
blagie [28]3 years ago
4 0
I think when it does not react with anything I think
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Consider the following reaction:
iren [92.7K]

Answer:

A. ΔG° = 132.5 kJ

B. ΔG° = 13.69 kJ

C. ΔG° = -58.59 kJ

Explanation:

Let's consider the following reaction.

CaCO₃(s) → CaO(s) + CO₂(g)

We can calculate the standard enthalpy of the reaction (ΔH°) using the following expression.

ΔH° = ∑np . ΔH°f(p) - ∑nr . ΔH°f(r)

where,

n: moles

ΔH°f: standard enthalpy of formation

ΔH° = 1 mol × ΔH°f(CaO(s)) + 1 mol × ΔH°f(CO₂(g)) - 1 mol × ΔH°f(CaCO₃(s))

ΔH° = 1 mol × (-635.1 kJ/mol) + 1 mol × (-393.5 kJ/mol) - 1 mol × (-1206.9 kJ/mol)

ΔH° = 178.3 kJ

We can calculate the standard entropy of the reaction (ΔS°) using the following expression.

ΔS° = ∑np . S°p - ∑nr . S°r

where,

S: standard entropy

ΔS° = 1 mol × S°(CaO(s)) + 1 mol × S°(CO₂(g)) - 1 mol × S°(CaCO₃(s))

ΔS° = 1 mol × (39.75 J/K.mol) + 1 mol × (213.74 J/K.mol) - 1 mol × (92.9 J/K.mol)

ΔS° = 160.6 J/K. = 0.1606 kJ/K.

We can calculate the standard Gibbs free energy of the reaction (ΔG°) using the following expression.

ΔG° = ΔH° - T.ΔS°

where,

T: absolute temperature

<h3>A. 285 K</h3>

ΔG° = ΔH° - T.ΔS°

ΔG° = 178.3 kJ - 285K × 0.1606 kJ/K = 132.5 kJ

<h3>B. 1025 K</h3>

ΔG° = ΔH° - T.ΔS°

ΔG° = 178.3 kJ - 1025K × 0.1606 kJ/K = 13.69 kJ

<h3>C. 1475 K</h3>

ΔG° = ΔH° - T.ΔS°

ΔG° = 178.3 kJ - 1475K × 0.1606 kJ/K = -58.59 kJ

5 0
3 years ago
Which of the following statements is subjective? Van Gogh painted beautiful works of art. The planets revolve around the sun. Bl
mezya [45]
The "Van Gogh" one is subjective, because it expresses opinion and is not a true, hard fact. :)
4 0
4 years ago
Read 2 more answers
If you have 12.5g of fluoride and 16.2g of sodium, which is the limiting reactant and how sodium fluoride in grams is your theor
Korvikt [17]

Answer:

F2 is the limiting reactant

27.6 grams of NaF is produced.

Explanation:

Balance the equation first.

2Na+ F2 ---> 2NaF

To find the limiting reactant, solve for how much NaF can be produced with Na and F2

12.5g F2 x (1 mole F2/ 38.00 grams F2)x (2 mole NaF/ 1 mole F2)

=0.658 moles NaF

16.2g Na x (1 mole Na/ 22.99 grams Na)x (2 mole NaF/ 2 mole Na)

=0.705 moles NaF

Since F2 produced the least NaF, F2 is the limiting reactant.

Now, to find how much NaF there is, use the moles solved above with F2 as the limiting reactant.

0.658 moles NaF x (41.99 grams NaF/ 1 mole NaF)= 27.6 moles NaF

27.6 moles of NaF would be theoretically produced.

8 0
3 years ago
Which of the following is an example of a chemical reaction?
nevsk [136]

Answer:

where is the option I can't see plz give the option first the I try to give answer

3 0
3 years ago
A student who stresses too much about his grades has incorrectly named an organic compound 3-propylhexane.
Brums [2.3K]

Answer:

None of these.

The correct answer should be, 4-ethylheptane.

Explanation:

In naming Alkanes, the general rules apply:

I. Identify the longest continuous carbon chain and name it as the root or parent name.

II. Identify any side chains and add their names and positions as a prefix to the parent chain.

III. When there are more than one type of side chain, name them alphabetically.

IV. Use hyphens between numbers and letters and commas between numbers.

V. Number your side chains to obtain the lowest number combinations possible.

For the above question,

first, attempt drawing only the carbon skeleton, of 3-propylhexane thus,

C-C-C-C-C-C

|

C-C-C

The longest continuous carbon chain (numbering from the top right) is 7 carbon atoms, hence, parent or root name is heptane. The 2 carbon atoms (at top left) not numbered make up the alkyl group called ethyl and since they are attached to carbon number 4 of the numbered carbon atoms ( whether the numbering is from top right to bottom right or vice versa ), their position and name should be written as a prefix to the parent name. That is why the organic compound is named, 4-ethylheptane.

Please note that in drawing the carbon skeleton of 3-propylhexane, the name is the same even if you start placing the bottom 3 carbon atoms on the 3rd carbon (top) from the left or from the right because the numbering can start from any side to achieve the lowest number combinations of numbering common Alkanes.

7 0
3 years ago
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