1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
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>
You might be interested in
What example of mixture could be seperated using two or more techniques? Explain your answer
STatiana [176]
You can take two liquids of different densities (how much mass is in a given volume) and pour them into a funnel. An example is oil and water. When the mixture settles, the denser liquid will be at the bottom, and drips through the funnel first. This is a separation that you can just let occur naturally.
8 0
2 years ago
What volume would 3.01•1023 molecules of oxygen gas occupy at STP?
Sliva [168]
First, find moles of oxygen gas: (3.01 x10^23 molec.)/(6.02 x10^23) =0.5mol O2


Second, multiply moles by the standard molar volume of a gas at STP:(0.5mol)(22.4L) = 11.2L O2
6 0
3 years ago
What is the concentration of OH − and pOH in a 0.00066 M solution of Ba ( OH ) 2 at 25 ∘ C? Assume complete dissociation.
Allushta [10]

<u>Answer:</u> The hydroxide ion concentration and pOH of the solution is 1.32\times 10^{-3}M  and 2.88 respectively

<u>Explanation:</u>

We are given:

Concentration of barium hydroxide = 0.00066 M

The chemical equation for the dissociation of barium hydroxide follows:

Ba(OH)_2\rightarrow Ba^{2+}+2OH^-

1 mole of barium hydroxide produces 1 mole of barium ions and 2 moles of hydroxide ions

pOH is defined as the negative logarithm of hydroxide ion concentration present in the solution

To calculate pOH of the solution, we use the equation:

pOH=-\log[OH^-]

We are given:

[OH^-]=(2\times 0.00066)=1.32\times 10^{-3}M

Putting values in above equation, we get:

pOH=-\log(1.32\times 10^{-3})\\\\pOH=2.88

Hence, the hydroxide ion concentration and pOH of the solution is 1.32\times 10^{-3}M  and 2.88 respectively

3 0
3 years ago
MgX2 Very low density Highly reactive Diatomic Using the periodic table, determine which element these characteristics MOST LIKE
photoshop1234 [79]
Oxygen, fluorine and iodine are diatomic elements. Flourine is more reactive than the other two because it is the closest away to filling its outer layer of electrons and becoming stable like a noble gas.
3 0
3 years ago
Read 2 more answers
Which statement is true about the patterns shown on the electromagnetic spectrum?
Rudiy27
A. As wavelength increases, radiant energy and frequency increase.
5 0
2 years ago
Other questions:
  • How are t cells and b cells same
    7·2 answers
  • The phase that is most likely to occur at high temperatures and high pressures is:
    13·1 answer
  • Chemists use activity series to determine wether which type of reaction will occur?
    7·1 answer
  • Which law states that the pressure and absolute temperature of a fixed quantity of gas are directly proportional under constant
    7·1 answer
  • How many moles in 206.91 g Na
    10·1 answer
  • Please help me school ends tomorrow
    6·1 answer
  • What type of bonds connect the bases to each other.
    8·2 answers
  • Chegg an insulated rigid tank contains 12 kg of air at 200 kpa and 500 c. The tank valve is opened, and pressure reduces to 75 k
    11·1 answer
  • How many moles of Hydrogen gas will be produced if you start with 2.5 moles of Magnesium and an excess of Hydrochloric Acid give
    14·1 answer
  • A change in _____ means that a chemical reaction has occurred. Responses A the energy and massthe energy and mass B the kinds of
    5·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!