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Simora [160]
3 years ago
15

What was the oxygen crisis

Chemistry
1 answer:
salantis [7]3 years ago
8 0
The Great Oxidation Event (GOE), sometimes also called the Great Oxygenation Event, Oxygen Catastrophe, Oxygen Crisis, Oxygen Holocaust,[2] or Oxygen Revolution, was a time period when the Earth's atmosphere and the shallow ocean first experienced a rise in oxygen, approximately 2.4 billion years ago (2.4 Ga) to 2.1–2.0 Ga during the Paleoproterozoic era.[3] Geological, isotopic, and chemical evidence suggests that biologically produced molecular oxygen (dioxygen, O2) started to accumulate in Earth's atmosphere and changed Earth's atmosphere from a weakly reducing atmosphere to an oxidizing atmosphere,[4] causing many existing species on Earth to die out.[5] The cyanobacteria producing the oxygen caused the event which enabled the subsequent development of multicellular forms.
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How many atoms are in a sample of 72.8 g calcium (Ca)?
xxMikexx [17]
Atomic mass Ca = 40.078 a.m.u

40.078 g -------------------- 6.02x10²³ atoms
72.8 g ---------------------- ??

72.8 x ( 6.02x10²³) / 40.078 =

4.38x10²⁵ / 40.078 = 1.093x10²⁴ atoms

hope this helps!
5 0
3 years ago
Read 2 more answers
PLS HELPPPP
Nady [450]

Answer:

1. First one is true : as per periodic table down the group , the elements has increasing order of shell & with that the London dispersion forces brings the inter-molecules close together and bromine converted into liquid .

2. second one is False  because carbon-carbon bonds are not weak bonds they form mutual covalent bonds which are stronger bonds and cannot be easily disrupted .

3. A single carbon atom has the valency of 4 so it can be bonded with four hydrogen atom at the same time .

Explanation:

5 0
3 years ago
You have 0.14 moles of sodium chloride (NaCl). How many grams do you have? ( 1 mole of NaCl = 58 grams NaCl) *
Step2247 [10]

Answer:

Option D is correct = 8.12 grams of NaCl

Explanation:

Given data:

Moles of sodium chloride = 0.14 mol

Mass of sodium chloride = ?

Solution:

Formula:

Number of moles = mass of NaCl / Molar mass of NaCl

Molar mass of NaCl = 58 g/mol

Now we will put the values in formula.

0.14 mol = Mass of NaCl / 58 g/mol

Mass of NaCl = 0.14 mol  ×  58 g/mol

Mass of NaCl = 8.12 g of NaCl

Thus, 0.14 moles of NaCl contain 8.12 g of NaCl.

4 0
3 years ago
What do elements in the first two columns of the periodic table have in common?
coldgirl [10]

Answer: b.) they tend to lose electrons to gain stability

Explanation:

5 0
3 years ago
In the presence of a base, blue litmus paper will .<br>O turn purple<br>stay blue<br>to turn red​
Inessa05 [86]

Answer:

In the presence of a base, blue litmus paper will turn red........

7 0
3 years ago
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