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3 years ago

6

What is Darwin's name for species that do not appear to have changed for millions of years?

1 answer:

ioda3 years ago

4 0

Since, the options have not been given the question is incomplete.

What is Darwin's name for species that do not appear to have changed for millions of years?

a.

Dinosaurs

b.

Living fossils

c.

Old souls

d.

Ancient moderns

Answer: b. Living fossil

Explanation:

In 1859 Charles Darwin proposed the term living fossil, that means a species or group of species that had not changed in terms of evolutionary context thus can be useful in tracing the extinct or previously existing forms of life. The examples of the living fossils are horseshoe crabs, ginkgo (Conifers) and tuatara. These group of animals were existed unchanged in the Ordovician, Permian, and Triassic periods respectively with few surviving species.

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That would be N2O4.

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If you feed 100 kg of N2 gas and 100 kg of H2 gas into a<br> reactor. What is the excess reactant?

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Answer:

H₂ gas

Explanation:

The reaction between nitrogen gas and hydrogen gas forms ammonia (the Haber-Bosch process):

N₂ + 3H₂ ⇒ 2NH₃

The excess reactant can be found by comparing the moles of nitrogen and hydrogen. The molar mass of N₂ is 28.00 g/mol and the molar mass of H₂ is 2.02 g/mol.

(100 kg N₂)(1000g/kg)(mol/28.00g) = 3570 mol

(100 kg H₂)(1000g/kg)(mol/2.02g) = 49500 mol

The molar ratio between the reactant N₂ and H₂ is 1N₂:3H₂. The moles of nitrogen required to react with H₂ is:

(49500 mol H₂)(1N₂ / 3H₂) = 16500 mol

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Be sure to answer all parts. Dimercaprol (HSCH2CHSHCH2OH) was developed during World War I as an antidote to arsenic-based poiso

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<u>Answer:</u>

<u>For A:</u> The number of arsenic atoms are $3.4\times 10^{21}$

<u>For B:</u> The percent composition of mercury, thallium and chromium in their complexes are 61.76 %, 62.2 % and 29.51 % respectively.

<u>Explanation:</u>

<u>For A:</u>

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

Given mass of dimercaprol = 696 mg = 0.696 g (Conversion factor: 1 g = 1000 mg)

Molar mass of dimercaprol = 124.21 g/mol

Putting values in above equation, we get:

$\text{Moles of dimercaprol}=\frac{0.696g}{124.21g/mol}=0.0056mol$

According to mole concept:

1 mole of a compound contains $6.022\times 10^{23}$ number of molecules.

So, 0.0056 moles of dimercaprol will contain $0.0056\times 6.022\times 10^{23}=3.4\times 10^{21}$ number of molecules.

As, 1 molecule of dimercaprol binds with 1 atom of Arsenic

So, $3.4\times 10^{21}$ number of dimercaprol molecules will bind with = $1\times 3.4\times 10^{21}=3.4\times 10^{21}$ number of arsenic atoms

Hence, the number of arsenic atoms are $3.4\times 10^{21}$

<u>For B:</u>

We know that:

Molar mass of dimercaprol = 124.21 g/mol

Molar mass of mercury = 200.59 g/mol

Molar mass of thallium = 204.38 g/mol

Molar mass of chromium = 51.99 g/mol

Also, 1 molecule of dimercaprol binds with 1 metal atom.

To calculate the percentage composition of metal in a complex, we use the equation:

$\%\text{ composition of metal}=\frac{\text{Mass of metal}}{\text{Mass of complex}}\times 100$ ......(1)

<u>For mercury:</u>

Mass of Hg-complex = (200.59 + 124.21) = 324.8 g

Mass of mercury = 200.59 g

Putting values in equation 1, we get:

$\%\text{ composition of mercury}=\frac{200.59g}{324.8g}\times 100=61.76\%$

<u>For thallium:</u>

Mass of Tl-complex = (204.38 + 124.21) = 328.59 g

Mass of thallium = 204.38 g

Putting values in equation 1, we get:

$\%\text{ composition of thallium}=\frac{204.38g}{328.59g}\times 100=62.2\%$

<u>For chromium:</u>

Mass of Cr-complex = (51.99 + 124.21) = 176.2 g

Mass of chromium = 51.99 g

Putting values in equation 1, we get:

$\%\text{ composition of chromium}=\frac{51.99g}{176.2g}\times 100=29.51\%$

Hence, the percent composition of mercury, thallium and chromium in their complexes are 61.76 %, 62.2 % and 29.51 % respectively.

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