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shutvik [7]
3 years ago
8

describe how astronomers are able to use the light from a distant star to determine what elements make up the stars.

Chemistry
1 answer:
dlinn [17]3 years ago
7 0

Answer:

The spectra of the Sun and stars exhibited bright and dark lines called Fraunhofer lines. These were shown to be caused by elements emitting or absorbing light at specific wavelengths. Because each element emits or absorbs light only at specific wavelengths, the chemical composition of stars can be determined.

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Archaeology has shown that ancient people _____.
Readme [11.4K]
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3 years ago
Read 2 more answers
True or false 4 questions help please!
Alekssandra [29.7K]

Answer:

Explanation:

True or false 4 questions help please!

Most mixtures are not physical changes.

True

False   FALSE  when I add solid NaCl salt to water I no longer have a solid salt, I have a solution of sodium and chlorid ions in liquid water.  this is  physical change

Chemical Changes do not create a new substance.

True

False  FALSE 0ne of the proofs that you have a chemical change is the presence of a new substance

Fire is an example of a Chemical Change.

True  TRUE  fire is oxygen reacting wiIh mattter to form new compounds

False

Explosions are not chemical changes.

It depends on the explosion  if I blow up a balloon until it POPS!! that is physical chame.  If I light a firecracker and it explodes, that is a chemical change of oxygen reacting with hot gunpowder

A change in color and odor are both examples of chemical changi

I would rewrite the question as  

A change in color and odor  both INDICATE a chemical change

and that is

True  TRUE

False

F

True   Fire is an example of a Chemical Change.

True

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False

5 0
2 years ago
What does Hess's law state can be done in order to be able to react solid magnesium with oxygen gas safely (that is, without exp
aleksley [76]

Answer:

C. The reaction can be broken down and performed in steps

Explanation:

Hess's Law of Constant Heat Summation states that irrespective of the number of steps followed in a reaction, the total enthalpy change for the reaction is the sum of all enthalpy changes corresponding to all the steps in the overall reaction. The implication of this law is that  the change of enthalpy in a chemical reaction is independent of the pathway between the initial and final states of the system.

To obtain MgO safely without exposing magnesium to flame, the reaction sequence shown in the image attached may be carried out. Since the enthalpy of the overall reaction is independent of the pathway between the initial and final states of the system, the sum of the enthalpy of each step yields the enthalpy of formation of MgO.

3 0
2 years ago
If a 45 mM phosphate solution(solution A) had an absorbance of 1.012. What would be the absorbance if 11 mL of solution A was us
timofeeve [1]

Answer:

0.550

Explanation:

The absorbance (A) of a substance depends on its concentration (c) according to Beer-Lambert law.

A = ε . <em>l</em> . c

where,

ε: absorptivity of the species

<em>l</em>: optical path length

A 45 mM phosphate solution (solution A) had an absorbance of 1.012.

A = ε . <em>l</em> . c

1.012 = ε . <em>l</em> . 45 mM

ε . <em>l</em>  = 0.022 mM⁻¹

We can find the concentration of the second solution using the dilution rule.

C₁ . V₁ = C₂ . V₂

45mM . 11mL = C₂ . 20.0 mL

C₂ = 25 mM

The absorbance of the second solution is:

A = (ε . <em>l</em> ). c

A = (0.022 mM⁻¹) . 25 mM = 0.55 (rounding off to 3 significant figures = 0.550)

8 0
3 years ago
The major reason for chemical bonding is _____.. . . for atoms to gain the stability of the octet. to form a substance in low su
Otrada [13]
In my opinion, the best answer among the choices listed above is the first option. The major reason for chemical bonding is <span>for atoms to gain the stability of the octet. In general, chemical reactions happen in order for substances achieve stability or appropriately achieve equilibrium.</span>
7 0
3 years ago
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