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mezya [45]
4 years ago
11

Which of these substances are compounds? How do you know?

Chemistry
1 answer:
tankabanditka [31]4 years ago
7 0
Salt because it's a solid and helium and nitrogen are gases.
Water is a liquid because it's form can change.
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A certain substance X has a normal freezing point of 5.6 °C and a molal freezing point depression constant Kf-7.78 °C-kg·mol-1.
Harrizon [31]

Answer:

27.60 g urea

Explanation:

The <em>freezing-point depression</em> is expressed by the formula:

  • ΔT= Kf * m

In this case,

  • ΔT = 5.6 - (-0.9) = 6.5 °C
  • Kf = 7.78 °C kg·mol⁻¹

m is the molality of the urea solution in X (mol urea/kg of X)

First we<u> calculate the molality</u>:

  • 6.5 °C = 7.78 °C kg·mol⁻¹ * m
  • m = 0.84 m

Now we<u> calculate the moles of ure</u>a that were dissolved:

550 g X ⇒ 550 / 1000 = 0.550 kg X

  • 0.84 m = mol Urea / 0.550 kg X
  • mol Urea = 0.46 mol

Finally we <u>calculate the mass of urea</u>, using its molecular weight:

  • 0.46 mol * 60.06 g/mol = 27.60 g urea

7 0
3 years ago
What will happen to the pressure inside of a jar when you suck out al of the air?Does it decrease or increase?
EleoNora [17]

Answer:

the pressure decreases because there is a sudden lack of air. some times, cans will crush if the air is sucked out; this is because the pressure on the outside is greater than the inside

7 0
3 years ago
Aldehydes may oxidize to form:
Arlecino [84]
Aldehydes may oxidize to form carboxylic acid <span>exception to oxidizing formaldehyde  with strong oxidizing agent.

HCHO + 3[O] = CO</span>₂ + H₂O
5 0
4 years ago
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What is the difference between sexual and asexual reproduction
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Asexual reproduction takes/or inherits one parent's genes, because it only involves one organism.
Sexual reproduction requires both a male and female. 
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3 years ago
Light ray 1 strikes the smooth surface, separating air and water as shown below. A horizontal line is drawn and the part above t
FinnZ [79.3K]

I think the correct answer is ray 2.

8 0
3 years ago
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