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Molodets [167]
3 years ago
9

Humans first appeared in the _____ period.

Chemistry
2 answers:
Ira Lisetskai [31]3 years ago
6 0

Answer:

They first appeared in the fossil record around 66 million years ago, soon after the Cretaceous–Paleogene extinction event that eliminated about three-quarters of plant and animal species on Earth, including most dinosaurs.

Explanation:

vlabodo [156]3 years ago
4 0

Answer:

A or b I learned this in history

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How could natural selection lead to speciation?
Harlamova29_29 [7]

Answer:

Speciation can be driven by evolution, which is a process that results in the accumulation of many small genetic changes called mutations in a population over a long period of time. ... Natural selection can result in organisms that are more likely to survive and reproduce and may eventually lead to speciation.

I hope it's helpful!

6 0
3 years ago
If a star of 50 solar masses were to supernova, it would most likely become a _____.
alexandr1967 [171]

The answer is Black Hole.

7 0
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NEED HELP NOW!!!!!!!
Afina-wow [57]

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fission

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3 years ago
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please hurry! If 3.87g of powdered aluminum oxide is placed in a container containing 5.67g of water, what is the limiting react
VikaD [51]

Answer:

Explanation:

Given parameters:

Mass of aluminium oxide = 3.87g

Mass of water = 5.67g

Unknown:

Limiting reactant = ?

Solution:

The limiting reactant is the reactant in short supply in a chemical reaction. We need to first write the chemical equation and convert the masses given to the number of moles.

Using the number of moles, we can ascertain the limiting reactants;

         Al₂O₃  + 3H₂O  →  2Al(OH)₃  

Number of moles;

            Number of moles = \frac{mass}{molar mass}

molar mass of Al₂O₃  = (2x27) + 3(16) = 102g/mole

    number of moles = \frac{3.87}{102}  = 0.04mole

   

molar mass of  H₂O = 2(1) + 16 = 18g/mole

    number of moles = \frac{5.67}{18}  = 0.32mole

From the reaction equation;

        1 mole of  Al₂O₃  reacted with 3 moles of H₂O

   0.04 mole of Al₂O₃ will react with 3 x 0.04 mole = 0.12 mole of H₂O

But we were given 0.32 mole of H₂O and this is in excess of amount required.

This shows that Al₂O₃ is the limiting reactant

           

6 0
3 years ago
In Balancing Equations, why do I put a 3 before reactant H?
Katena32 [7]
You have 3 (h2(so4)) on the reactants side so you need to have 6 total hydrogen’s on the products side. Therefore 3(h2) is required.
5 0
3 years ago
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