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iren2701 [21]
3 years ago
8

Are pure substances chemically combined​

Chemistry
1 answer:
dmitriy555 [2]3 years ago
4 0

Pure substances can or can not be chemically combined.

Pure substances can be either elements or compounds, but not mixture. Mixture are different substances mixing together without being chemically combined, such as air, which is a mixture of oxygen, carbon dioxide, water etc. Mixture can be separated by physical methods, like filtration or decantation.

Meanwhile, elements are the substances that cannot be further separated by any means. No matter physical or chemical methods. Examples of elements are oxygen, hydrogen, neon and all the other ones from the periodic table. Compounds are basically elements joining together, but they’re chemically combined which means their electrons (kind of subatomic particle) are either shared or given away. These elements can only be separated by chemical methods like electrolysis or heating.

Therefore, as long as the substance cannot be separated by physical methods, it can be considered as a pure substance. We can now conclude that pure substance can be (element) or can not be (compound) chemically combined.

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Distinguish between dunes and loess
agasfer [191]

Answer:

Dunes are loose sand hills.

Loess is a compacted wind-blown formation of sediment.

Explanation:

Sand dunes are, as their name implies, made of sand which is itself made of tiny quartz pieces. Sand dunes are present where there is a ready source of broken down sandstone or other type of rock and wind to transport the sand. The dunes are mobile and loose and migrate over time.

Loess comes in vast formations and was created in a very different way. In the last ice age, winds from the north carried sediments loosened and ground by glaciers southwards. There, the sediments accumulated in large formations and became compacted over time.

6 0
3 years ago
What is the ph of a 0.45 m solution of aniline (c6h5nh2)? (pkb  9.40)?
mote1985 [20]

Answer is: pH of aniline is 9.13.<span>
Chemical reaction: C</span>₆H₅NH₂(aq)+ H₂O(l) ⇌ C₆H₅NH₃⁺(aq) + OH⁻(aq).

pKb(C₆H₅NH₂) = 9.40.

Kb(C₆H₅NH₂) = 10∧(-9.4) = 4·10⁻¹⁰.

c₀(C₆H₅NH₂) = 0.45 M.

c(C₆H₅NH₃⁺) = c(OH⁻) = x.

c(C₆H₅NH₂) = 0.45 M - x.

Kb = c(C₆H₅NH₃⁺) · c(OH⁻) / c(C₆H₅NH₂).

4·10⁻¹⁰ = x² /  (0.45 M - x). 

Solve quadratic equation: x = c(OH⁻) = 0.0000134 M.

pOH = -log(0.0000134 M.) = 4.87.

pH = 14 - 4.87 = 9.13.

7 0
3 years ago
What is the percent lithium in lithium nitrate?
seropon [69]

Answer:

Around 60%

Explanation:

4 0
3 years ago
What is the pH of a 0.00530 M solution of HCI?
MrMuchimi

Answer:

2.28

Explanation:

HCl(l) ===> H+ + cl-

HCl is a very strong acid. Almost all of it will decompose to the right. That means the concentration of H+ is 0.00530

pH = - log [H+]

pH = - log[0.00530]

pH = - - 2.2757

pH = 2.2757

Rounded this 2.28

5 0
3 years ago
What’s the physical properties of a molecular solid, in regards to its physical properties of formation?
Anastasy [175]
It has a fixed mass
it does not change with the shape of the container
it cannot be compressed
it has fixed atom and molecules and limited to very small displacement
only vibrational motion occur in the molecules of solid .
7 0
3 years ago
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