I am really confused

Pleaseeeeeee helpppppppp meeeeeeee

Darina [25.2K]

appear; disappear

im not 100% sure if thats what is being asked, but they fit and are true

3 0

3 years ago

Be sure to answer all parts.

Aleks04 [339]

Answer:

pH = 3.215

Explanation:

From the given information;

Using the equation for the dilution of a stock solution:

Since moles of C5H5N = moles of HNO3

Then:

$M_{C_5H_5N}\times V_{C_5H_5N}= M_{HNO_3}\times V_{HNO_3}$

$0.0750 M \times 2.65 L = 0.407 M \times V_{HNO_3}$

$V_{HNO_3}= \dfrac{0.0750 M \times 2.65 L}{0.407 M}$

$V_{HNO_3}=488.33 \ mL$

The reaction between C5H5NH and H2O is as follows:

$C_5H_5N^+H + H_2O$ ⇄ $C_5H_5N + H_3O^+$

$Molarity \ of \ C_5H_5N^+H = \dfrac{moles}{addition \ of\ the\ total\ volume}$

$Molarity \ of \ C_5H_5N^+H = \dfrac{0.0750 \ M \times 2.65 \ L}{2.65 \ L + 0.48833 \ L}$

$Molarity \ of \ C_5H_5N^+H = \dfrac{0.19875 \ ML}{3.13833 L }$

$= \ 0.06333\ M$

Now, the next step is to draw out the I.C.E table.

$C_5H_5N^+H + H_2O$ ⇄ $C_5H_5N + H_3O^+$

I 0.06333 0 0

C - x x x

E 0.06333 -x x x

$K_a = \dfrac{10^{-14}}{1.7 \times 10^{-19}} \\ \\ K_a = 5.8824 \times 10^{-6}$

$K_a = \dfrac{[C_5H_5N][H_3O^+] }{[C_5H_5N^+H] } \\ \\ 5.8824 \times 10^{-6} = \dfrac{x^2}{0.06333 - x}$

Assuming x < 0.06333

$x^2 = 5.8824 \times 10^{-6} \times 0.06333$

Then

$x^2 = 3.72532392 \times 10^{-7} \\ \\ x= \sqrt{3.72532392 \times 10^{-7}} \\ \\ x = 6.1035 \times 10^{-4} \ M$

$[H_3O^+] = x = 6.1035 \times 10^{-4} \ M \\ \\ pH = -log (6.1035 \times 10^{-4}) \\ \\ \mathbf{\\ pH = 3.215}$

6 0

3 years ago

What allowed the earth’s atmosphere to increase in oxygen concentration?

Sophie [7]

Answer:The answer is tiny organisms known as cyanobacteria, or blue-green algae.

Explanation:

These microbes conduct photosynthesis: using sunshine, water and carbon dioxide to produce carbohydrates and oxygen increase. Additionally, some sources you could use that I used to answer this question was

https://www.scientificamerican.com/article/origin-of-oxygen-in-atmosphere/

3 0

3 years ago

13. Which hormone does the thymus secrete?

zvonat [6]

Answer: G. thymosin and thymopoietin

Explanation:

The thymus produces and secretes thymosin, a hormone necessary for T cell development and production. The thymus is special in that, unlike most organs, it is at its largest in children. Once you reach puberty, the thymus starts to slowly shrink and become replaced by fat.

5 0

3 years ago

Distinguish between directional, stabilizing, and disruptive selection. Give examples.

pashok25 [27]

Directional selection is a type of natural selection that favors one extreme phenotype over the mean or another extreme. Examples of directional selection include giraffes that have long necks and the darkening of London's peppered moths after the Industrial Revolution.

Stabilizing selection, also known as purifying selection, is a type of natural selection in which genetic diversity decreases as the population stabilizes on a particular trait value. An example of stabilizing selection is birth weigh in humans.

Disruptive selection is a type of natural selection that shows a preference toward the reproduction of genetic material at the extremes within a population.One of the most studied examples of disruptive selection is the case of London's peppered moths.
From Wikipedia
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5 0

3 years ago