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Answer:

1) The percentage of oxygen in dry air is _______

C. 21

2) The composition of the Earth’s earliest atmosphere was different to that of the present atmosphere. Which of these gases was present in large amounts in the Earth’s earliest atmosphere?

B. CARBON DIOXIDE

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Answer: The percentage of oxygen in dry air is .  21

Explanation:  Ammonia gases was present in large amounts  in the easth7s earliest atmosphere

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Answer:

A

Explanation:

Coupled reactions are reactions in which endergonic reactions obtain the energy to go forward from exergonic reactions.

When benzene diazonium chloride interacts with phenol, the para position of the phenol molecules is associated with the diazonium salt, resulting in

p-hydroxyazobenzene. The coupling reaction is the name given to this process.

Answer:

the S.I unit

Explanation:

is the best unite

Answer:

179.5 feet

Explanation:

54.718 m converted to 179.5 feet.

Answer:

that the water is blue because of the way water absorbs light, the way particles in the water scatter light, and also because some of the blue light from the sky is reflected

Answer:

true

false

false

true

false

true

true

false

false

true

true

Answer:

a

Explanation:

I'm not completely sure tho veary sorry if it's wrong

Answer:

the answer is C

Explanation:

as the yeast feeds on sugar and yields the ATP per glucose molecule and Carbon dioxide

Answer:

the process by which green plants and some other organisms use sunlight to synthesize nutrients from carbon dioxide and water. Photosynthesis in plants generally involves the green pigment chlorophyll and generates oxygen as a by-product.

Answer:

the process by which green plants and some other organisms use sunlight to synthesize nutrients from carbon dioxide and water. Photosynthesis in plants generally involves the green pigment chlorophyll and generates oxygen as a by-product.

Answer:

C

Explanation:

like charges repel each others so if they have the same charge they will move away from each other

Answer:

I think option two (2) is the correct answer

Answer:

Thus, the element containing the greatest number of atoms is 12 g He. Thus, the correct option is (4) 12 g He. Note: The number of atoms of a compound is Avogadro's number for 1 mole of compound. The number 6.022×1023 is known as Avogadro's number.

Explanation:

(4)✔️ 12 g He

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Answer:

120gram I think so this is the answer if the answer is correct plz mark me as brainliest.

Explanation:

The easiest method to separating magnets is to slide them apart. When separating magnets keep in mind shear force. Magnets are measured on pull strength, so are up to five times easier to move if they are pushed apart instead of pulled apart. Small magnets slide relatively easily, even without spacers.

Firmly slide them away from each other and far enough apart so that they don't hop back together. Neodymium magnets are quite strong.

The properties of the magnet are:

Thus,  slide them away from each other and far enough apart so that they don't hop back together.

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Answer:

Ca + Pb(NO3)2 → Pb + Ca(NO3)2

Explanation:

This is an oxidation-reduction (redox) reaction:

PbII + 2 e- → Pb0

(reduction)

Ca0 - 2 e- → CaII

(oxidation)

Pb(NO3)2 is an oxidizing agent, Ca is a reducing agent.

Answer: The molecular weight of the dibasic acid is 89.6 g/mol

Explanation:

Normality is defined as the amount of solute expressed in the number of gram equivalents present per liter of solution. The units of normality are eq/L. The formula used to calculate normality:

[tex]\text{Normality}=\frac{\text{Given mass of solute}\times 1000}{\text{Equivalent mass of solute}\times \text{Volume of solution (mL)}}[/tex]      ....(1)

We are given:

Normality of solution = [tex]\frac{1}{20}=0.05N[/tex]

Given mass of solute = 0.56 g

Volume of solution = 250 mL

Putting values in equation 1, we get:

[tex]0.05=\frac{0.56\times 1000}{\text{Equivalent mass of solute}\times 250}\\\\\text{Equivalent mass of solute}=\frac{0.56\times 1000}{0.05\times 250}=44.8g/eq[/tex]

Equivalent weight of an acid is calculated by using the equation:

[tex]\text{Equivalent weight}=\frac{\text{Molar mass}}{\text{Basicity}}[/tex]   .....(2)

Equivalent weight of acid = 44.8 g/eq

Basicity of an acid = 2 eq/mol

Putting values in equation 2, we get:

[tex]44.8g/eq=\frac{\text{Molar mass}}{2eq/mol}\\\\\text{Molar mass}=(44.8g/eq\times 2eq/mol)=89.6g/mol[/tex]

Hence, the molecular weight of the dibasic acid is 89.6 g/mol

Answer:

XY bond is the least polar

Explanation:

Given

[tex]W = 1.0[/tex]

[tex]X = 2.0[/tex]

[tex]Y = 2.5[/tex]

[tex]Z = 3.5[/tex]

Required

The least polar bond

First, we calculate the difference in the electronegativities

[tex]WX = X - W[/tex]

[tex]WX = 2.0 - 1.0[/tex]

[tex]WX = 1.0[/tex]

[tex]WY = Y - W[/tex]

[tex]WY =2.5 - 1.0[/tex]

[tex]WY =1.5[/tex]

[tex]WZ =Z-W[/tex]

[tex]WZ =3.5 - 1.0[/tex]

[tex]WZ =2.5[/tex]

[tex]XY = Y -X[/tex]

[tex]XY = 2.5 -2.0[/tex]

[tex]XY = 0.5[/tex]

[tex]XZ = Z -X[/tex]

[tex]XZ = 3.5 -2.0[/tex]

[tex]XZ = 1.5[/tex]

[tex]YZ = Z - Y[/tex]

[tex]YZ = 3.5 - 2.5[/tex]

[tex]YZ = 1.0[/tex]

The least of the above calculations will be the least polar.

Hence, XY is the least polar

Answer:

Diatomic molecules contain two atoms that are chemically bonded. If the two atoms are identical, as in, for example, the oxygen molecule (O2), they compose a homonuclear diatomic molecule, while if the atoms are different, as in the carbon monoxide molecule (CO), they make up…

Explanation:

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Answer:

Describe what is happening within the system when it is at equilibrium in terms of concentrations, reactions that occur, and reaction rates.

Explanation:

The chemical equilibrium state is the state where the rate of forward reaction becomes equal to the rate of backward reaction.

At this stage the change in concentration of reactants becomes equal to the change in concentration of products.

The reaction will never cease.

That is the reason chemical equilibrium is called dynamic equilibrium.

So, forward and backward reactions will be taking place continuously at equal rates.

Answer:

this is because of collisions of molecules present in that particular system.

Explanation:

For instance, when air is filled in a balloon then the number of the molecules of air inside the balloon increases. As a result more collisions of molecules take place with the walls. This gives rise to high air pressure on the walls which causes the balloon to expand and get inflated.

Answer:

b

Explanation:

Molecular formula of Decanoic Acid is  C₁₀H₂₀O₂ therefore Option A is the right answer.

Decanoic Acid is a C10 , straight chain , saturated fatty acid . Its general formula is C₁₀H₂₀O₂ .

In the first option we can see a straight chain , saturated fatty acid and the molecular formula is also same as decanoic acid .

In second option the molecular formula is C₉H₁₈O₂ which is not same as Decanoic Acid.

Hence option A is the right answer.

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Answer: A decrease in population due to health threats is a possible consequence of decreasing air quality resulting from global warming.

Explanation:

When average temperature of Earth keeps on increasing for a longer period of time due to greenhouse gases, increased level of carbon dioxide and other gases etc then it is called global warming.

As humans use oxygen to sustain which is present in the air. So, when there will occur decrease in air quality that results from global warming then it means more illness or diseases will be there.

Hence, people will tend to die more often because of decrease in the air quality their health is getting affected.

Thus, we can conclude that a decrease in population due to health threats is a possible consequence of decreasing air quality resulting from global warming.

Answer:

A decrease in population due to health threats is a possible consequence of decreasing air quality resulting from global warming.

Explanation:

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Answer:

answers:

1.b

2.d

3.b

4. c

5.c

6.d

7.c

Explanation:

I think this is the correct answer pls mark brainliest and like..

19. place moth balls in the closet and observe after several days.

20. whenever wax or a candle burns it turns from solid to liquid but again at room temperature it turns to solid

21. evaporation, condensation, precipitation

22. it produces new substances

23. vinegar Bubbles when baking soda is added.

24. steam

Answer:

Los dos óxidos que forma el cobre son óxido de cobre (I) y óxido de cobre (II) (Cu₂O y CuO, respectivamente).

Explanation:

El cobre posee dos estados de oxidación más comunes, los cuales son +1 y +2.

En contacto con aire el cobre se puede oxidar para dar lugar al óxido cuproso u óxido de cobre (I):

4Cu + O₂ → 2Cu₂O

Dicha oxidación también puede dar lugar a la formación del óxido cúprico u óxido de cobre (II):

2Cu + O₂ → 2CuO

La formación del óxido cúprico se favorece a temperaturas mayores a la del ambiente (por encima de los 300 °C).

Por lo tanto, los dos óxidos que forma el cobre son óxido de cobre (I) y óxido de cobre (II) (Cu₂O y CuO, respectivamente).  

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Answer:

b is your answer...........

Answer:

Narcotics

I think ans is

Explanation:

tropicaia

Ecstasy, also known as MDMA, is used recreationally, so it can be called a club drug. However, it is illegal in the US, so it would be considered a narcotic as well. The effects it has are also of the stimulant variety, so they would fall under that category as well. It is definitely not a depressant.