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spayn [35]
3 years ago
10

Which of the following statements does not accurately describe Precambrian Earth?

Chemistry
2 answers:
8_murik_8 [283]3 years ago
6 0

Answer:

C. The ocean water was salty and rich in dissolved oxygen.  

Explanation:

The oldest and longest of the Geological Ages, the Pre-Cambrian extends from the formation of the Earth, approximately 4.5 billion years ago, to 570 million years ago.

This period begins with the formation of the Earth about 4.5 billion years ago, where the Earth was an incandescent mass with rivers of dissolved rock, erupting volcanoes and large amount of sulfur. The atmosphere was initially similar to the atmosphere of Mars and Venus and was composed of nitrogen, ammonia, hydrogen, carbon monoxide, methane and water vapor, expelled by volcanoes, and no sign of oxygen.

After 700 million years, most of the rocks on the surface of the earth had already been cooled and a large amount of water had condensed into an ocean. Even so, the volcanic eruptions were still constant and were giving rise to several islands that were pushed toward each other by the movement of the mantle. In this period small unicellular beings in the ocean begin to appear, the primitive algae and bacteria that assimilate the carbon dioxide of the atmosphere transforming it into free oxygen, slowly changing the composition of the atmosphere that, in that period, was composed basically by nitrogen and steam of Water. They are of this period the oldest fossils of the earth.

Ilya [14]3 years ago
3 0

c. the ocean water was salty and rich in dissolved oxygen

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Aspirin sun thesis Green Chemistry and Assime the aspirin is prepared by the following reaction and that 10.09. of salicylic aci
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<u>Answer:</u> The percentage yield of aspirin is 38.02 %.

<u>Explanation:</u>

To calculate the number of moles, we use the equation:

\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}      .....(1)

  • <u>For salicylic acid:</u>

Given mass of salicylic acid (C_7H_6O_3) = 10.09 g

Molar mass of salicylic acid (C_7H_6O_3) = 138.12 g/mol

Putting values in equation 1, we get:

\text{Moles of salicylic acid}=\frac{10.09g}{138.12g/mol}=0.0730mol

The chemical equation for the formation of aspirin follows:

C_7H_6O_3+C_4H_6O_3\rightarrow C_9H_8O_4+CH_3COOH

As, acetic anhydride is present in excess. So, it is considered as an excess reagent.

Thus, salicylic acid is a limiting reagent because it limits the formation of products.

By Stoichiometry of the reaction:

1 mole of salicylic acid produces 1 mole of aspirin.

So, 0.0730 moles of salicylic acid will produce = \frac{1}{1}\times 0.0730=0.0730mol of aspirin

Now, calculating the mass of aspirin from equation 1, we get:

Molar mass of aspirin = 180.16 g/mol

Moles of aspirin = 0.073 moles

Putting values in equation 1, we get:

0.073mol=\frac{\text{Mass of aspirin}}{180.16g/mol}\\\\\text{Mass of aspirin}=13.15g

To calculate the percentage yield of aspirin, we use the equation:

\%\text{ yield}=\frac{\text{Experimental yield}}{\text{Theoretical yield}}\times 100

Experimental yield of aspirin = 5.0 g

Theoretical yield of aspirin = 13.15 g

Putting values in above equation, we get:

\%\text{ yield of aspirin}=\frac{5.0g}{13.15g}\times 100\\\\\% \text{yield of aspirin}=38.02\%

Hence, the percent yield of aspirin is 38.01 %.

6 0
3 years ago
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