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3 years ago

What types of evidence do scientists use to determine evolutionary relationships among groups

1 answer:

5 0

There are several things that can help scientists evaluate which category something belongs to. The similarity in features is one of them. If two skulls looked alike, they were probably species of the same evolutionary category. For example say humans and monkeys rather than humans and dogs.
Similarly fossils have helped scientists categorise species. Study of the chromosomes (in cases with available chromosomes) can help scientists figure out a lot about the subjects and categorise them.

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Which liquid has the highest vapor pressure at 75°C?

Temka [501]

Answer:

1) Ethanol

Explanation:

If we will have interactions we will need more energy to break them in order to go from liquid to gas. If we need more energy, therefore, the temperature will be higher.

In this case, we can discard the propanone because this molecule don't have the ability to form hydrogen bonds. (Let's remember that to have hydrogen bonds we need to have a hydrogen bond to a heteroatom, O, N, P or S).

Then we have to analyze the hydrogen bonds formed in the other molecules. For ethanol, we will have only 1 hydrogen bond. For water and ethanoic acid, we will have 2 hydrogen bonds, therefore, we can discard the ethanol.

For ethanoic acid, we have 2 intramolecular hydrogen bonds. For water we have 2 intermolecular hydrogen bonds, therefore, the strongest interaction will be in the ethanoic acid.

The closer boiling point to the 75ºC is the ethanol (boiling point of 78.8 ºC) therefore these molecules would have enough energy to break the hydrogen bonds and to past from liquid to gas.

4 0

3 years ago

What is the difference between pioneer species and climax communities

bonufazy [111]

Pioneer species are the first species to arrive in an area after succession (hope this helped because i dont know about climax communities)

5 0

3 years ago

With reference to He-4 (or the diagram), explain the term isotopes.

boyakko [2]

Answer:

Isotopes are basically atoms of an element that have an unequal number of neutrons and protons. Of course the proton number remains the same, but the neutron number either decreases or increases, which leads to an overall change in mass. However, no chemical properties of the atom/element are changed as the electrons are the same number and do not react. In regards to Helium 4, the original number of neutrons in Helium is 2, and protons 2 as well. We see an equal number of neutrons and protons, hence an unchanged mass, and the element is not an isotope.

6 0

3 years ago

2) what is the mass of 6.02 x 1023 atoms of arsenic?

zzz [600]

Data:
Arsenic Molar Mass = 74,9216 ≈ 75 u (atomic mass unit)

Solving:

1 mole of arsenic → 75g ------------ 6,02*10²³ molecules
..................................X -------------- 1 molecule

6,02*10²³X = 75
$x = \frac{75}{6,02*10^{23}}$
$\boxed{x \approx 1,24*10^{24}grams}$

6 0

3 years ago

What is the percent composition of carbon in heptane c7h16

Gnom [1K]

Answer: the percent composition of carbon in heptane is 83.9%

Explanation:

1) Atomic masses of the atoms:

C: 12.01 g/mol

H: 1.008 g/mol

2) Molar mass of heptane:

C₇H₁₆: 7 × 12.01 g/mol + 16×1.008 g/mol = 100.2 g/mol

3) Mass of carbon in one mole of heptane:

C₇: 7 × 12.01 g/mol = 84.07 g/mol

3) Percent composition of carbon:

% = (mass in grams of C) / (mass in grams of C₇H₁₆) × 100 =

= (84.07 g/ 100.2 g) × 100 = 83.9% ← answer

8 0

3 years ago