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inessss [21]
4 years ago
6

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

Chemistry
1 answer:
ad-work [718]4 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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% Yield (10 points): 8. Using the reaction above: a. Calculate the theoretical yield of the product if you started with 5 grams
vekshin1

Answer:

a) m = 7.9 g

b) m = 3.002 g

c) butyl MgBr

Explanation:

First, you are not providing the reaction, so if difficult to solve this without it. However, I manage to find a similar question so I'm gonna solve this on basis with that question. The picture attached has the question and reaction.

Now, according to the image we have a wittig reaction. Which is commonly used to convert an aldehyde into an alcohol. As we can see in the picture, the reaction starts with hexanal and butyl MgBr (Grignard reagent) in acid medium. This gives as a product the 5-pentanol.

Let's write again the reaction here:

C₆H₁₂O + C₄H₉MgBr -----------> C₁₀H₂₂O + OHMgBr

We can see that the reaction is perfectly balanced so we don't need to balance. And we also can see that we have a mole ratio of 1:1 between the reactants and the products, which means that the calculated moles of either one reactant or the other, would be the same moles of the products.

To calculate moles, and afterward, the yield, we need the molecular weight of all compounds:

MM C₆H₁₂O = 100 g/mol

MM C₄H₉MgBr = 161.32 g/mol

MM C₁₀H₂₂O = 158 g/mol

With this given MM, let's calculate the theorical yield of the product in each case:

<u>a) 5 grams of aldehyde</u>

In this case, let's calculate the moles of the given aldehyde:

moles = 5 / 100 = 0.05 moles

Assuming this is the limiting reagent, the moles of the aldehyde would be the same moles of the product, so:

moles aldehyde = moles product = 0.05 moles

So the theorical yield would be:

m product = 0.05 * 158

<h2>m = 7.9 g of C₁₀H₂₂O</h2>

<u>b) 3 grams of butyl MgBr</u>

In this case, we will do the same thing as before, and we will assume that this is limiting reagent so:

moles = 3 / 161.32 = 0.019 moles

m C₁₀H₂₂O = 0.019 * 158

<h2>m C₁₀H₂₂O = 3.002 g</h2>

<u>c) limiting reagent</u>

Now this is easier, because if we have 5 g of aldehyde and 3 g of grignard reagent, we already has the moles of each with these masses, therefore, as both starting materials have a 1:1 mole ratio, we can see that the moles of the aldehyde are higher than the moles of grignard agent, therefore, the limiting reagent would be the butyl MgBr while the aldehyde would be the excess.

<h2>Limiting reagent = Butyl MgBr</h2>

Hope this helps

4 0
3 years ago
You have a particle of length 68 nm. What is this in meters? ( need help asap)
Bess [88]

Answer:

B

Explanation:

4 0
3 years ago
What is the approximate pH of a 0.06 M solution of CH3COOH (given that Ka = 1.78 x 10-5)? 1 3 6 7 9
DedPeter [7]
The answer would come out as 3
6 0
4 years ago
Read 2 more answers
All of the alkali earth metals, Group 2, have two valence electrons. Which of these would represent the oxidation number of the
juin [17]
Your answer should be C.) +2. "All the elements in Group 2 have two electrons in their valence shells, giving them an oxidation state of +2." 


Credits: https://chem.libretexts.org/Core/Inorganic_Chemistry/Descriptive_Chemistry/Elements_Organized_by_Blo...

Hopefully this has helped! :)
5 0
3 years ago
Calcium+Hydrochloric acid=
mezya [45]

Answer:

You get Ca(II)H^2

Explanation:

This is a reaction type equation calcium reacts with HA and forms a bond.

6 0
3 years ago
Read 2 more answers
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