Ask question

Ask question

All categories

3 years ago

9

When an atom gives off energy in the form of light, a. it becomes excited. b. it becomes more stable. c. it returns to ground st

ate. d. both b & c e. none of the above.

1 answer:

egoroff_w [7]3 years ago

6 0

Answer is only B.
<span>it becomes more stable</span>

You might be interested in

If you have access to stock solutions of 1.00 M H3PO4, 1.00 M of HCl, and 1.00 M NaOH solution, (and distilled water of course),

garri49 [273]

Answer:

0.10L of 1.00M of H₃PO₄ and 0.1613L of 1.00M NaOH

Explanation:

The pKa's of phosphoric acid are:

H₃PO₄/H₂PO₄⁻ = 2.1

H₂PO₄⁻/HPO₄²⁻ = 7.2

HPO₄²⁻/PO₄³⁻ = 12.0

To make a buffer with pH 9.40 we need to convert all H₃PO₄ to H₂PO₄⁻ and an amount of H₂PO₄⁻ to HPO₄²⁻

To have a 50mM solution of phosphoures we need:

2L * (0.050mol / L) = 0.10 moles of H₃PO₄

0.10 mol * (1L / mol) = 0.10L of 1.00M of H3PO4

To convert the H₃PO₄ to H₂PO₄⁻ and to HPO₄²⁻ must be added NaOH, thus:

H₃PO₄ + NaOH → H₂PO₄⁻ + H₂O + Na⁺

H₂PO₄⁻ + NaOH → HPO₄²⁻ + H₂O + Na⁺

Using H-H equation we can find the amount of NaOH added:

pH = pKa + log [A⁻] / [HA] <em>(1)</em>

<em>Where [A-] is conjugate base, HPO₄²⁻ and [HA] is weak acid, H₂PO₄⁻</em>

<em>pH = 7.40</em>

<em>pKa = 7.20</em>

[A-] + [HA] = 0.10moles <em>(2)</em>

Replacing (2) in (1):

7.40 = 7.20 + log 0.10mol - [HA] / [HA]

0.2 = log 0.10mol - [HA] / [HA]

1.5849 = 0.10mol - [HA] / [HA]

1.5849 [HA] = 0.10mol - [HA]

2.5849[HA] = 0.10mol

[HA] = 0.0387 moles = H₂PO₄⁻ moles

That means moles of HPO₄²⁻ are 0.10mol - 0.0387moles = 0.0613 moles

The moles of NaOH needed to convert all H₃PO₄ in H₂PO₄⁻ are 0.10 moles

And moles needed to obtain 0.0613 moles of HPO₄²⁻ are 0.0613 moles

Total moles of NaOH are 0.1613moles * (1L / 1mol) = 0.1613L of 1.00M NaOH

Then, you need to dilute both solutions to 2.00L with distilled water.

4 0

2 years ago

HELP ASAP! Chemical reactions involving liquids only will be influenced by ALL of the following EXCEPT: a) temperature of the sy

Rom4ik [11]

<span>Chemical reactions involving only liquids will be influenced by ALL of the following EXCEPT: </span><span><span>c) size of reactant particles d) pressure of the system.

</span>Reason:
1) As per Arrhenius theory, rate of chemical reactions is influence by temperature. Mathematically it is expressed as: k = A exp(-Ea/RT)
</span>where, k = rate constant, A = collision frequency, Ea = activation energy, T = temp. From above relation, it can be seen that, chemical reactions involving only liquids will be influenced temperature.

2) Also, if know that, rates of chemical reactions is mathematically expressed as: $Rate = [A]^{x} B^{y}....$ ,
where A, B, .. are the reactants.
From above relation, it can be seen that, chemical reactions involving only liquids will be influenced concentration i.e. number of particle.

3) However, since all the reactant and catalyst used (if any) is in liquid state, particle size of same will not influence the reaction.

4) Also, since there are no gas-phase reactant, pressure will not affect the reaction.

8 0

2 years ago

Acetone is one of the most important solvents in organic chemistry. It is used to dissolve everything from fats and waxes to air

Phantasy [73]

Answer:

The half-life time, the team equired for a quantity to reduce to half of its initial value, is 79.67 seconds.

Explanation:

The half-life time = the time required for a quantity to reduce to half of its initial value. Half of it's value = 50%.

To calculate the half-life time we use the following equation:

[At]=[Ai]*e^(-kt)

with [At] = Concentration at time t

with [Ai] = initial concentration

with k = rate constant

with t = time

We want to know the half-life time = the time needed to have 50% of it's initial value

50 = 100 *e^(-8.7 *10^-3 s^- * t)

50/100 = e^(-8.7 *10^-3 s^-1 * t)

ln (0.5) = 8.7 *10^-3 s^-1 *t

t= ln (0.5) / -8.7 *10^-3 = 79.67 seconds

The half-life time, the team equired for a quantity to reduce to half of its initial value, is 79.67 seconds.

4 0

3 years ago

What happens to the cell membrane during exocytosis?

Cloud [144]

Answer:

Endocytosis and Exocytosis: Differences and Similarities

ARTICLE Apr 28, 2020

by Nicole Gleichmann

Endocytosis and Exocytosis: Differences and Similarities

Endocytosis and exocytosis are the processes by which cells move materials into or out of the cell that are too large to directly pass through the lipid bilayer of the cell membrane. Large molecules, microorganisms and waste products are some of the substances moved through the cell membrane via exocytosis and endocytosis.

Why is bulk transport important for cells?

Cell membranes are semi-permeable, meaning they allow certain small molecules and ions to passively diffuse through them. Other small molecules are able to make their way into or out of the cell through carrier proteins or channels.

But there are materials that are too large to pass through the cell membrane using these methods. There are times when a cell will need to engulf a bacterium or release a hormone. It is during these instances that bulk transport mechanisms are needed.

Endocytosis and exocytosis are the bulk transport mechanisms used in eukaryotes. As these transport processes require energy, they are known as active transport processes.

Vesicle function in endocytosis and exocytosis

During bulk transport, larger substances or large packages of small molecules are transported through the cell membrane, also known as the plasma membrane, by way of vesicles – think of vesicles as little membrane sacs that can fuse with the cell membrane.

Cell membranes are comprised of a lipid bilayer. The walls of vesicles are also made up of a lipid bilayer, which is why they are capable of fusing with the cell membrane. This fusion between vesicles and the plasma membrane facilitates bulk transport both into and out of the cell.

What is endocytosis? Endocytosis definition and purposes

Endocytosis is the process by which cells take in substances from outside of the cell by engulfing them in a vesicle. These can include things like nutrients to support the cell or pathogens that immune cells engulf and destroy.

Endocytosis occurs when a portion of the cell membrane folds in on itself, encircling extracellular fluid and various molecules or microorganisms. The resulting vesicle breaks off and is transported within the cell.

8 0

2 years ago

Explain Charles law

kodGreya [7K]

"Charles Law" is the relationship between "volume-temperature" (V ∝ T).

<u>Explanation</u>:

Charles Law is basically volume-temperature relationship (V ∝ T). French scientist “Jacques Charles” in 1787 studied effect of temperature on the volume of gases at constant pressure, which described how gases manage to expand when heated. Law stated as “At constant pressure, the volume of a given "mass" of a gas decreases or increases by 1/273 of its volume at $0^{\circ} \mathrm{C}$ for each one degree rise or fall in temperature”. Formula derived from law is as follows: $\mathbf{V}_{\mathbf{t}}=\mathbf{V}_{0}[\mathbf{1}+\mathbf{t} / \mathbf{2} 7 \mathbf{3}]$ here ${V}_{0}$ is volume of given mass of a gas at $0^{\circ} \mathrm{C}$ , ${V}_{t}$ is its volume at any temperature $t^{\circ} \mathrm{C}$ . Application of Charles law is hot air balloons.

8 0

2 years ago