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
Can somebody help me wit dis?
Hatshy [7]

Answer:

it is D

Explanation:

6 0
3 years ago
By increasing the length of heat exchanger, the effectiveness and cold stream output temperature of the heat exchanger
Dominik [7]

Answer:

Effectiveness and cold stream output temperature of the heat exchange Increases. So, Answer is b) Increases.

Explanation:

We have a heat exchanger, and it is required to compare the effectiveness and cold stream output if the length is increased.

Heat exchangers are engineering devices used to transfer energy. Thermal energy is transferred from Fluid 1 - Hot fluid (HF) to a Fluid 2 - Cold Fluid (CF). Both fluids 1 and 2 can flow with different values of mass flow rate and different specific heat. When the streams go inside the heat exchanger Temperature of Fluid 1 (HF) will decrease, at the same time Temperature of the Fluid 2 (CF) will increase.

In this case, we need to analyze the behavior taking into account different lengths of heat exchangers. If the length of the heat exchanger increases, it means the transfer area will increases. Heat transfer will increase if the transfer area increases. In this sense, the increasing length is the same than increase heat transfer.

If the heat transfer increases, it means Fluid 1 (HF) will reduce its temperature, and at the same time Fluid 2 (CF) will increase its temperature.

Finally, Answer is b) Effectiveness and cold stream output temperature increases when the length of the heat exchanger is increased.

5 0
3 years ago
Knowing the chemical properties of a substance will tell you how the substance
ratelena [41]
<span>Whereas physical properties of a substance tells us about how the substance looks, smells, etc, the chemical properties of a substance basically tells us how the substance will react with other substances. Therefore, knowing the chemical property of a substance tells us how the substance reacts with others.Hope this helps. Let me know if you need additional help!</span><span />
8 0
3 years ago
Read 2 more answers
What is the molarity (M) of chloride ions in a solution prepared by mixing 155 ml of 0.276 M calcium chloride with 384 ml of 0.4
sesenic [268]

Answer: The concentration of Cl^- ions in the resulting solution is 1.16 M.

Explanation:

To calculate the molarity of the solution after mixing 2 solutions, we use the equation:

M=\frac{n_1M_1V_1+n_2M_2V_2}{V_1+V_2}

where,

n_1,M_1\text{ and }V_1 are the n-factor, molarity and volume of the CaCl_2

n_2,M_2\text{ and }V_2 are the n-factor, molarity and volume of the AlCl_3

We are given:

n_1=2\\M_1=0.276M\\V_1=155mL\\n_2=3\\M_2=0.471M\\V_2=384mL  

Putting all the values in above equation, we get

M=\frac{(2\times 0.276\times 155)+(3\times 0.471\times 384)}{155+384}\\\\M=1.16M

The concentration of Cl^- ions in the resulting solution will be same as the molarity of solution which is 1.16 M.

Hence, the concentration of Cl^- ions in the resulting solution is 1.16 M.

6 0
3 years ago
A mineral that breaks into irregular pieces is said to show which of the following?
Ray Of Light [21]
The original options for this question were cleavage, luster and hardness. The answer would be cleavage.
4 0
3 years ago
Read 2 more answers
Other questions:
  • What are the main categories of sedimentary rock?
    10·1 answer
  • Why are the trends and exceptions to the trends in ionization energy observed? Check all that apply. Ionization energy tends to
    8·2 answers
  • Explain how temperature can affect the speed of reaction. Give an example.
    15·1 answer
  • What is produced when a base reacts with water?
    13·1 answer
  • In a particular type of cat, coat color follows the dominant/recessive pattern of inheritance. The allele for a brown coat (B) i
    5·1 answer
  • The atomic mass of boron is 10.811. What is the mass number of the most
    8·1 answer
  • Find odd one out for (Air,salt solution,sandwich)​
    6·1 answer
  • A student is investigating acceleration using balls with
    13·1 answer
  • What does the law of multiple proportion account for?
    8·1 answer
  • the deltag value for the acontinase reaction is 5.8 kj/mol. what is the ratio of isocitrate/citrate understandard conditions?
    13·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!