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lorasvet [3.4K]
3 years ago
8

When coal is burned to generate electricity, 70% of the primary energy in the coal is transformed into unused heat. This means t

hat the energy conversion efficiency from chemical to electrical energy is _____
Chemistry
1 answer:
Vinvika [58]3 years ago
5 0

Answer:

0.3

Explanation:

<u>The energy conversion efficiency is defined as the ratio of the useful output energy being generated by an energy machine to the input energy.It is denote by η.</u>

The input and the useful output can be electric power, chemical, mechanical power, heat, etc.

<u>Coal is being burnt to generate energy. Let the the input energy of coal be x units.</u>

The energy lost in unused heat = 70% of x = 0.7x units

Useful output energy = 100% - 70% = 30% of x = 0.3x units

Thus,

η = Useful Energy/ Input energy

<u>η = 0.3x/x = 0.3</u>

Thus,

<u>The energy conversion efficiency from chemical to electrical energy is 0.3.</u>

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Gasoline and kerosene (specific gravity 0.820) are blended to obtain a mixture with a specific gravity of 0.770. Calculate the v
Dmitrij [34]

Answer:

The volumetric ratio is 0,71

Explanation:

Let's begin with the equation:

Db = Mb/Vb (1)

Where:

Db: Blend Density, Mb: Blend Mass and Vb: Blend Volume

And we know: Vb = Vg + Vk (2)

Where:

Vg: Gasoline Volume and Vk: Kerosene Volume

Therefore replacing (2) into (1):

Db = (Mg + Mk) / (Vg + Vk)

Db = (Dg * Vg + Dk * Vk)/(Vg + Vk) (3)

Where:

Dg: Gasoline Density and Dk: Kerosene Density

The specific gravity is defined as:

SG = Substance Density / Reference Density

Therefore:

Db = SGb * Dref\\Dg = SGg * Dref\\Dk = SGk * Dref

Where:

Dref: Reference Density

SGb: Blend Specific Gravity

SGg: Gasoline Specific Gravity (which is 0.7 approximately)

SGk: Kerosene Specific Gravity

Replacing these equations into (3) we get:

SGb * Dref = (SGg * Dref * Vg + SGk * Dref * Vk)/(Vg + Vk)

SGb * Dref = Dref * (SGg * Vg + SGk * Vk)/(Vg + Vk)

SGb = (SGg * Vg + SGk * Vk)/(Vg + Vk)

SGb * (Vg + Vk) = SGg * Vg + SGk * Vk

SGb * Vg + SGb* Vk = SGg * Vg + SGk * Vk

Replacing with the Specific Gravity data, we obtain:

0.77 * Vg + 0.77 * Vk = 0.7 * Vg + 0.82 * Vk

0.77 * Vg - 0.7 * Vg = 0.82 * Vk - 0.77 * Vk

0.07 * Vg = 0.05 * Vk

Vg/Vk = 0.05/0.07

Vg/Vk = 0.71

8 0
3 years ago
(LO 37,45) A reaction is 75% complete in 45.0 min. How long after its start will the reaction be 50% complete if it is (A) first
seropon [69]

Answer:

A) t = 22.5 min and B) t = 29.94 min

Explanation:

Initial concentration, [A]₀ = 100

Final concentration = 100 -75 = 25

Time = 45 min

A) First order reaction

ln[A] − ln[A]₀ = −kt

Solving for k;

ln[25] − ln[100] = - 45k

-1.386 = -45k

k = 0.0308 min-1

How long after its start will the reaction be 50% complete?

Initial concentration, [A]₀ = 100

Final concentration, [A] = 100 -50 = 50

Time = ?

ln[A] − ln[A]₀ = −kt

Solving for k;

ln[50] − ln[100] = - 0.0308 * t

-0.693 = -0.0308 * t

t = 22.5 min

B) Zero Order

[A] = [A]₀ − kt

Using the values from the initial reaction and solving for k, we have;

25 = 100 - k(45)

-75 = -45k

k = 1.67 M min-1

How long after its start will the reaction be 50% complete?

Initial concentration, [A]₀ = 100

Final concentration, [A] = 100 -50 = 50

Time = ?

[A] = [A]₀ − kt

50 = 100 - (1.67)t

-50 = - 1.67t

t = 29.94 min

3 0
3 years ago
PLSS HELP! The gas carbon dioxide is a pure substance. Which of the following is true about carbon dioxide? (4 points)
Nadusha1986 [10]

Answer:

The answer is option A..

5 0
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Given that kb for c6h5nh2 is 1.7 × 10-9 at 25 °c, what is the value of ka for c6h5nh3 at 25 °c?
lina2011 [118]

Answer: k_a for C_6H_5NH_3^+ at 25°C is 0.588\times 10^{-4}

Explanation: We are given k_b of C_6H_5NH_2 at 25°C which is 1.7\times 10^{-9}

To calculate the k_a of C_6H_5NH_3^+, we use the formula:

k_w=k_a\times k_b

k_w\text{ at }25^o=1\times 10^{-14}

Putting values in above equation, we get:

1\times 10^{-14}=k_a\times (1.7\times 10^{-9})\\k_a=0.588\times 10^{-5}

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3 years ago
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Alisiya [41]

Answer:

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