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Effectus [21]
3 years ago
7

The standard heats of formation for CO2(g), C2H6(g), and H2O(l) are -394.0 kJ/mol, -84.00 kJ/mol, and -286.0 kJ, respectively. W

hat is the standard heat of reaction for the following process? C2H6(g) + 7/2 O2(g) --> 2CO2(g) + 3H2O(l)
Chemistry
1 answer:
Ivanshal [37]3 years ago
6 0

Answer:

ΔH°r = -1562 kJ

Explanation:

Let's consider the following combustion.

C₂H₆(g) + 7/2 O₂(g) ⇒ 2 CO₂(g) + 3 H₂O(l)

We can calculate the standard heat of reaction (ΔH°r) using the following expression:

ΔH°r = ∑np × ΔH°f(p) - ∑nr × ΔH°f(r)

where,

ni are the moles of reactants and products

ΔH°f(i) are the standard heats of formation of reactants and products

The standard heat of formation of simple substances in their most stable state is zero. That means that ΔH°f(O₂(g)) = 0

ΔH°r = ∑np × ΔH°f(p) - ∑nr × ΔH°f(r)

ΔH°r = [2 mol × ΔH°f(CO₂) + 3 mol × ΔH°f(H₂O)] - [1 mol × ΔH°f(C₂H₆) + 7/2 mol × ΔH°f(O₂)]

ΔH°r = [2 mol × (-394.0 kJ/mol) + 3 mol × (-286.0 kJ/mol)] - [1 mol × (-84.00 kJ/mol) + 7/2 mol × 0]

ΔH°r = -1562 kJ

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The answer is Radiation

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2) At equilibrium, both the forward and reverse reactions are still occurring.

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A serving of Cheez-Its releases 1.30 x 10^4 kcal (1 kcal = 4.18 kJ) when digested by your body. If this same amount of energy we
kondor19780726 [428]

Answer:

The final temperature is:- 7428571463.57 °C

Explanation:

The expression for the calculation of heat is shown below as:-

Q=m\times C\times \Delta T

Where,  

Q  is the heat absorbed/released

m is the mass

C is the specific heat capacity

\Delta T  is the temperature change

Thus, given that:-

Mass of water = 1.75 mg = 0.00175 g ( 1 g = 0.001 mg)

Specific heat of water = 4.18 J/g°C

Initial temperature = 35 °C

Final temperature = x °C

\Delta T=(x-35)\ ^0C/tex]
Q = [tex]1.3\times 10^4 kcal

Also, 1 kcal = 4.18 kJ = 4.18\times 10^3 J

So, Q = 1.3\times 10^4\times 4.18\times 10^3 J = 54340000 J

So,  

54340000=0.00175\times 4.18\times (x-35)

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x=7428571463.57

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3 0
2 years ago
According to the law of conservation of mass, if an element A has an atomic mass of 2 mass units and element B has an atomic mas
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The law of conservation of mass states that mass is neither created nor destroyed. Since we have 2 g/mol of A and 3 g/mol of B then AB should be equal to the sum of their molar mass that is 

2 g/mol + 3 g/mol = 5 g/mol AB

for the case of A2B3

A2 = 2 * 2 = 4 g/mol
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5 0
3 years ago
3) Calculate the percent by mass of 3.55 g NaCl dissolved in 88 g water.
kotykmax [81]

Answer:

The percent by mass of 3.55 g NaCl dissolved in 88 g water is 3.88%

Explanation:

When a solute dissolves in a solvent, the mass of the resulting solution is a sum of the mass of the solute and the solvent.

A percentage is a way of expressing a quantity as a fraction of 100. In this case, the percentage by mass of a solution is the number of grams of solute per 100 grams of solution and can be represented mathematically as:

Percent by mass=\frac{mass of solute}{mass of solution} *100

In this way it allows to precisely establish the concentration of solutions and express them in terms of percentages.

In this case:

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Replacing:

Percentbymass=\frac{3.55}{91.55}*100

Percent by mass= 3.88%

<u><em>The percent by mass of 3.55 g NaCl dissolved in 88 g water is 3.88%</em></u>

5 0
3 years ago
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