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inessss [21]
3 years ago
6

When did oxygen first appear in earth's atmosphere??

Chemistry
1 answer:
ad-work [718]3 years ago
7 0
<span> the atmosphere holds about 21 per cent oxygen. Over the Earth’s 4.6 billion year history, oxygen did not appear in the atmosphere until perhaps about 2.5 billion years ago. Since then, oxygen levels have fluctuated in tandem with global geological and biological events, such as mass extinctions.</span>
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Which of the following reactions would be predicted by the activity series list
den301095 [7]

Answer:

it's a D answer if it's wrong please can you understand my question please

3 0
3 years ago
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It isn't possible to transfer heat from an object at a lower temperature to another object at a _ temperature unless work is don
lisov135 [29]
Higher. Because this type of heat transfer is conduction, meaning that heat always transfers to cooler objects.
5 0
3 years ago
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Which molecule has the greatest difference in electronegativity (DE) between the two different elements? A. CO_2 B. H_2S C. NH_3
Natalka [10]

Answer:

Water has the greatest ΔEN

ΔEN H₂O → 3.4 - 2.1 = 1.3   Option D.

Explanation:

We should find the Electronegativity data in the Periodic table for all the elements:

C : 2.6

O: 3.4

H: 2.1

S: 2.6

N: 3.0

a. ΔEN CO₂ → 3.4 - 2.6 = 0.4

b. ΔEN H₂S → 2.6 - 2.1 = 0.5

c. ΔEN NH₃ → 3 - 2.1= 0.9

d. ΔEN H₂O → 3.4 - 2.1 = 1.3

3 0
3 years ago
Calcium oxide or quicklime (CaO) is used in steelmaking, cement manufacture, and pollution control. It is prepared by the therma
Elena-2011 [213]

Answer:

The yearly release of CO_2 into the atmosphere is 6.73\times 10^{10} kg.

Explanation:

CaCO_3(s)\rightarrow CaO(s) + CO_2(g)

Annual production of CaO = 8.6\times 10^{10} kg=8.6\times 10^{13} g

Moles of CaO :

\frac{8.6\times 10^{13} g}{56 g/mol}=1.53\times 10^{12} moles

According to reaction, 1 mole of CaO is produced along with 1 mole of carbon-dioxide.

Then along with  1.53\times 10^{12} moles of CaO moles of carbon-dioxide moles produced will be:

\frac{1}{1}\times 1.53\times 10^{12} moles=1.53\times 10^{12} moles of carbon-dioxide

Mass of 1.53\times 10^{12} moles of carbon-dioxide:

1.53\times 10^{12}mol\times 44 g/mol=6.73\times 10^{13} g =6.73\times 10^{10} kg

The yearly release of CO_2 into the atmosphere is 6.73\times 10^{10} kg.

6 0
3 years ago
A gaseous system undergoes a change in temperature and volume. What is the entropy change for a particle in this system if the f
viva [34]

Answer: -2.373  x 10^-24J/K(particles

Explanation: Entropy is defined as the degree of randomness of a system which is a function of the state of a system and depends on the number of the random microstates present.

The entropy change for a particle in a system  depends on the initial and final states of a system and is given by Boltzmann equation as  

S = k ln(W) .

where S =Entropy

K IS Boltzmann constant ==1.38 x 10 ^-23J/K

W is the number of microstates available to the system.

 The  change in entropy is given as

S2 -S1 = kln W2 - klnW1

dS = k ln (W2/W1)

where w1 and w2 are initial and final microstates

from the question, W2(final) = 0.842 x W1(initial), so:

= 1.38*10-23 ln (0.842)

=1.38*10-23  x -0.1719

= -2.373  x 10^-24J/K(particles)

4 0
3 years ago
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