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liq [111]
2 years ago
5

Which of the following is an example of a pure substance? *

Chemistry
1 answer:
Natali [406]2 years ago
3 0

Answer:

Iron shavings

Explanation:

A substance that has a fixed chemical composition throughout and a mixture is when two or more substances are combined, but they are not combined chemically.

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Urea, (NH2)2CO, is a product of metabolism of proteins. An aqueous solution is 37.2% urea by mass and has a density of 1.032 g/m
Feliz [49]

Answer:

The molarity of urea in this solution is 6.39 M.

Explanation:

Molarity (M) is <em>the number of moles of solute in 1 L of solution</em>;  that is

molarity = moles of solute ÷ liters of solution

To calculate the molality, we need to know the number of moles of urea and the volume of solution in liters. We assume 100 grams of solution.

Our first step is to calculate the moles of urea in 100 grams of the solution,

using the molar mass a conversion factor. The total moles of 100g of a 37.2 percent by mass solution is

60.06 g/mol ÷ 37.2 g = 0.619 mol

Now we need to calculate the volume of 100 grams of solution, and we use density as a conversion factor.

1.032 g/mL ÷ 100 g = 96.9 mL

This solution contains 0.619 moles of urea in 96.9 mL of solution. To express it in molarity, we need to calculate the moles present in 1000 mL (1 L) of the solution.

0.619 mol/96.9 mL × 1000 mL= 6.39 M

Therefore, the molarity of the solution is 6.39 M.

4 0
3 years ago
If atoms are made of smaller parts such as electrons, why are atoms considered the basic unit of matter?
arsen [322]
Firstly, atoms are also composed of protons and neutrons as well as electrons.

Now, to answer your question... Atoms are the smallest you can go while still having it be an element, hence the definition ''<span>the basic unit of a chemical element.'' It is the smallest unit that has the chemical properties of an element. However, atoms still need these charges to be atoms. Without electrons, they'd just be ions. Hope this helps.</span>
8 0
3 years ago
Which of these humans activities is a serious threat to marine ecosystems
Paraphin [41]

Answer:

Pollution, non native species being introduced, and other human activities

Explanation:

Human activities affect marine ecosystems as a result of pollution, overfishing, the introduction of invasive species,and acidification, which all impact on the marine food web and may lead to largely unknown consequences for the biodiversity and survival of marine life forms.

5 0
2 years ago
Read 2 more answers
What is the half life of the graphed material?
daser333 [38]

Answer:

3 hours

Explanation:

To know the the correct answer to the question given above, it is important we know the definition of half-life.

The half-life of a substance is simply defined as the time taken for half the substance to decay.

Considering the diagram given above, the initial mass of the substance is 100 g.

Half of the initial mass = 100 / 2 = 50 g

Now, we shall determine the time from the graph taken to get to 50 g.

Considering the diagram given above, the time taken to get to 50 g is 3 hours.

Therefore, the half-life of the material is 3 hours.

3 0
3 years ago
Which will most likely happen if an appropriate enzyme is added to a chemical reaction
Sliva [168]
It could explode

or blow up


hope it helped
5 0
3 years ago
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