A chemist needs 0.550 mol selenium for a reaction. What mass of selenium should a chemist use?
*show work and giving brainliest*

Answer:

6.502 x 10²⁴ atoms.

Explanation:

First we convert 158.4 g of CO₂ into moles, using carbon dioxide's molar mass:

Then we calculate how many CO₂ molecules are there in 3.6 moles, using Avogadro's number:

As there are 3 atoms per CO₂ molecule, we triple the number of CO₂ molecules in order to get the answer:

The closest answer is the third option,  6.502 x 10²⁴ atoms.

Answer:

According to the kinetic molecular theory of gases, the average speed and kinetic energy of gas molecules would INCREASE.

Explanation:

In the kinetic molecular theory of gases, assumptions were made based on macroscopic properties of gas (pressure, volume and temperature) which are as a result of the microscopic properties like the position and the speed of the gas molecules. The kinetic molecular theory explains the behaviour of gases through the following 5 assumptions made about an ideal gas;

--> Molecules of a gas are in constant and rapid motion in straight lines until they collide with one another and with the walls of their containers.

--> The actual volume occupied by the had is negligible compared with the volume of the container.

--> Forces of attraction or repulsion between the molecules of a gas are negligible

--> The collision between the molecules is perfectly elastic.

--> The average kinetic energy of the gas molecules is proportional to the temperature of the gas.

Because gas molecules are in constant motion, it has kinetic energy which can be altered when there is increase in pressure. An increase in pressure will cause gas molecules to collide more frequently with one another. This in turn leads to increase in average speed and the kinetic energy of the individual molecules.

Explanation:

Nuclear power plants deliver electricity 24 hours a day, 7 days a week, irrespective of weather and seasons. As well as reducing greenhouse gas emissions, nuclear generation helps reduce air pollution

Answer:

D

Explanation:

Just did the test

Answer:

The answer is in the problem

Explanation:

As general rule of number of oxygen is -2:

O → -2

Alkali metals (Li, Na, K) are always +1

Na → +1

Alkali earth methals (Be, Mg, Ca...) are always +2

Ca → +2

The halogen group (F, Cl, Br...) is always -1

F → -1

The oxidation number of Si (+/- 4)

Aluminium is, usually +3

And to complete the octet rule in nitrogen, 3 electrons are required. That means:

N → -3

Answer: (a) Mole fraction of [tex]H_{2}[/tex] is 0.66.

Mole fraction of [tex]N_{2}[/tex] is 0.33

(b) The partial pressure of [tex]H_{2}[/tex] is 1.98 atm.

The partial pressure of [tex]N_{2}[/tex] is 0.99 atm.

(c) The total pressure is 3.0 atm

Explanation:

Given: Volume = [tex]22.4 dm^{3}[/tex]  (1 [tex]dm^{3}[/tex] = 1 L) = 22.4 L

Moles of [tex]H_{2}[/tex] = 2.0 mol

Moles of [tex]N_{2}[/tex] = 1.0 mol

Total moles = (2.0 + 1.0) mol = 3.0 mol

Temperature = 273.15 K

[tex]PV = nRT\\[/tex]

where,

P = pressure

V = volume

n = number of moles

R = gas constant = 0.0821 L atm/mol K

T = temperature

Substitute the values into above formula as follows.

[tex]PV = nRT\\P \times 22.4 L = 3.0 mol \times 0.0821 L atm/mol K \times 273.15 K\\P = 3.0 atm[/tex]

The mole fraction of [tex]H_{2}[/tex] is calculated as follows.

[tex]Mole fraction = \frac{moles of H_{2}}{moles of H_{2} + moles of N_{2}}\\= \frac{2.0 mol}{(2.0 + 1.0) mol}\\= 0.66[/tex]

The mole fraction of [tex]N_{2}[/tex] is as follows.

[tex]Mole fraction = \frac{moles of N_{2}}{moles of H_{2} + moles of N_{2}}\\= \frac{1.0 mol}{(2.0 + 1.0) mol}\\= 0.33[/tex]

Partial pressure of [tex]H_{2}[/tex] are as follows.

[tex]P_{H_{2}} = P_{total} \times mole fraction of H_{2}\\= 3.0 atm \times 0.66\\= 1.98 atm[/tex]

Partial pressure of [tex]N_{2}[/tex] are as follows.

[tex]P_{N_{2}} = P_{total} \times mola fraction of N_{2}\\= 3.0 atm \times 0.33\\= 0.99 atm[/tex]

Answer: yes they come in different colors.

Explanation:

Most shades of soil is mostly black,brown,red,gray,and white the color of soil and other properties including texture, structure, and consistency are used to distinguish and identify soil.

Answer:

Rubidium and cesium

Explanation:

It is noteworthy to say here that larger cations have more stable superoxides. This goes a long way to show that large cations are stabilized by large cations.

Let us consider the main point of the question. We are told in the question that the reason why potassium reacts with oxygen to form a superoxide is because of its low value of first ionization energy.

The implication of this is that, the other two metals that can be examined to prove this point must have lower first ionization energy than potassium. Potassium has a first ionization energy of 419 KJmol-1, rubidium has a first ionization energy of 403 KJ mol-1 and ceasium has a first ionization energy of 376 KJmol-1.

Hence, if we want to validate the hypothesis that potassium's capacity to form a superoxide compound is related to a low value for the first ionization energy, we must also consider the elements rubidium and cesium whose first ionization energies are lower than that of potassium.

Answer:

2,6–dimethylcyclohexanol

Explanation:

To name the compound given in the question above, we must first obtain the following:

1. Determine the functional group of the compound.

2. Locate the longest continuous carbon chain.

3. Identify the substituent group attached to the compound.

4. Locate the position of the substituent group.

5. Combine the above to obtain the name of the compound.

Now, we shall determine the name IUPAC name of the compound. This can be obtained as follow:

1. The compound contains the –OH group. Thus, the compound is an alcohol.

2. The compound is a cyclic compound with six carbon forming the ring. Thus, the parent name of the compound is cyclohexane. Thus, the presence of the –OH group changes the parent name of the compound to cyclohexanol.

3. The substituent group attached to the compound is methyl (–CH₃)

NOTE: There are two –CH₃ groups attached to the compound.

4. The position of the 1st –CH₃ group is at carbon 2, while the 2nd is at carbon 6.

NOTE: Counting is done from the carbon bearing the functional group.

5. Therefore, the name of the compound is:

2,6–dimethylcyclohexanol

Answer:

Gymnosperm and Angiosperms both are plant groups but Gymnosperm is just very large leaves that come out of the ground and Angiosperms have flowers. Gymnosperm produce seeds in pine cones for example. Some plants in the Gymnosperm group of plants are pines. They produce naked seeds which means that they aren't protected by a ovary (Fruit like an apple) to help them get planted. Angiosperms have seeds that come out of their flowers and are called covered seeds. When the plant is about to die, it's seeds fall out and either float away and grow later of fall where the plant is. Also, insects carry them places too.

Hope this helps.

Answer:

B.Urea

Explanation:

When an amino acid is broken down, the nitrogen it contains is converted into urea by the liver which then is excreted via the kidneys.

Answer:

urea

Explanation:

when u eat proteins the body breaks them down into amino acids . Ammonia is produced from leftover amino acids and it must be removed from the body. the liver produces many chemicals (enzymes) that change ammonia into a form called ureas

Answer:

False

Explanation:

Answer:

every 4 years we add an extra day, February 29th, to our calendars these extra days called leave days help synchronize our human created calendars with us orbit around the sun and the actual passing of our seasons

Answer:

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=> First Aid enables you to assist persons who become injured in the event of an accident or emergency situation until help arrives.

[tex] \huge\blue{ \mid{ \underline{ \overline{ \tt Situations :- }} \mid}}[/tex]

=> If an accident happens in the workplace, in your home or in a public space, you can use the help of a first aid kit.

=> In situations such as when someone ingests a harmful substance, suffers from a heart attack, a seizure or stroke, is involved in a motor vehicle accident or is caught in a natural disaster, a person trained and knowledgeable in even the very basics of First Aid can be of extreme importance in assisting the injured person(s) until emergency responders arrive.

Answer:

hi

Explanation:

I'm just figuring this out

Answer:

Explanation:

Here we'll use our formula for specific heat, Q=mcΔT.

Q= Heat (Joules), m=mass (g), c=specific heat

ΔT= (final temperature - initial temperature)

When we add a heated piece of metal in water at a lower temperature, the metal will lose heat and the water will absorb that heat. Over time they will eventually reach an equilibrium, here we have it at 21.9 C. If you recall in thermodynamics, , when we lose heat it is exothermic and the values of exothermic reactions are negative, and the values of endothermic reactions are positive. So we can say the heat of the metal is exothermic and releasing heat into the water until they reach equilibrium, thus they are equal. Keeping in mind Q= heat,

-Q metal = Q water.

We can expand this equation to -mcΔT= mcΔT.

Our equation reflects what is happening to the metal and the water.

Before we start, it might be helpful to remember that the

c=specific heat of water= 4.186 J/g C

Let's plug in what we know and solve for c=specific heat of metal. I'll start with the left side then go to the right side.

-(23.9g)(c)(29.9-97.8) = (52.4g)(4.184)(29.9 - 21.9)

-(23.9gc)(29.9-97.8) = (52.4g)(4.184)(29.9 - 21.9)

-(23.9g)(c)(-67.9) = (52.4g)(4.184)(29.9 - 21.9)

1623c = (52.4g)(4.184)(29.9 - 21.9)

1623c = (52.4g)(4.184)(8)

1623c = 1754

c= [tex]\frac{1754}{1623}[/tex]

c= 1.08

This means it takes less heat to raise the temperature of the piece of metal ( in comparison to the water, which require more ).

The question is incomplete, the complete question is;

A student determines the number of moles of water in a

hydrated metal oxide by weighing a clean, dry crucible

and lid while the crucible is empty, then reweighing the

crucible and lid with a sample of the hydrate, heating the

crucible and lid with a Bunsen burner and then

reweighing the crucible and lid with the sample after

cooling to room temperature. Which error will result in

too high a value for the amount of water of hydration?

(A) The heating is conducted only once instead of the

three times recommended by the procedure.

(B) The lid is left off the crucible when it is weighed

with the hydrated oxide.

(C) The metal oxide reacts partially with oxygen in the

air, forming a compound in a higher oxidation state.

(D) Some of the heated oxide is spilled from the crucible

before it can be weighed.

Answer:

(D) Some of the heated oxide is spilled from the crucible

before it can be weighed.

Explanation:

It is possible to determine the number of moles of water in a hydrated metal oxide by weighing a clean, dry crucible and lid while the crucible is empty, then reweighing the crucible and lid with a sample of the hydrate. The crucible and lid with the sample are heated, cooled and reweighed.

As this process is going on, suppose some of the heated oxide is spilled from the crucible, then the mass of heated or anhydrous oxide decreases leading to a consequent increase in the number of moles of water in the hydrated metal oxide, hence the answer above.

The too high a value for the amount of water of hydration error is occur due to heating of given hydrated sample.

Hydrated compounds are those compounds in which water molecule is present with the normal compound.

To get the correct value of weight of hydrated compound, first we have to weigh the empty crucible and lid and then with sample of compound in the crucible and lid. After this substract empty weigh of crucible & lid from the sample-crucible-lid weigh. If we substract the weigh from heated sample crucible and lid, then we get the error because the hydrated water molecule may decompose due to heating and moles of water increases.

Hence, error will occur if we heat the sample.

To know more about hydrated compound, visit the below link:

https://brainly.com/question/16275027

Answer:

In a physical change the appearance or form of the matter changes but the kind of matter in the substance does not. However in a chemical change, the kind of matter changes and at least one new substance with new properties is formed.

Answer:

H₂(g) + F₂(g) ⇒ 2 HF(g)   ΔH°rxn = -542 kJ

Explanation:

Let's consider the unbalanced equation that occcurs when H₂(g) reacts with F₂(g) to form HF(g).

H₂(g) + F₂(g) ⇒ HF(g)

In order to get the balanced equation, we will multiply HF(g) by 2.

H₂(g) + F₂(g) ⇒ 2 HF(g)

To convert a balanced equation into a thermochemical equation, we need to add the standard enthaply of the reaction, considering that 542 kJ of energy are evolved for each mole of H₂(g) and there is 1 mole of H₂(g) in the balanced equation. By convention, when energy is released, it takes a negative sign. The thermochemical equation is:

H₂(g) + F₂(g) ⇒ 2 HF(g)   ΔH°rxn = -542 kJ

Answer:

Far as I know coefficients are unitless. sorry if this don't help ;)

Answer:

Venus

Explanation:

Similar in structure and size to Earth, Venus spins slowly in the opposite direction from most planets. Its thick atmosphere traps heat in a runaway greenhouse effect, making it the hottest planet in our solar system with surface temperatures hot enough to melt lead.

Answer:

Venus

Explanation:

Hope helps

Answer:

1.19 is the answer

Explanation:

Answer:

P-block

Explanation:

Chlorine

Atomic number (Z) 17

Group group 17 (halogens)

Period period 3

Block p-block

Answer:

What does "in which block does chlorine lies"? That question has no way to answer it because there is no question content lol

Explanation:

FeCl2 + Na2CO3 = FeCO3 + 2NaCl

Answer:

0.5875L

Explanation:

concentration = mole/ volume

n(LiCl) = 20 / (7 + 35.5) = 0.47 mol

volume = mole / conc.

volume = 0.47 /0.8

= 0.5875 dm³ = 0.5875L

Answer:

a < c < b < d

Explanation:

The weak acid with the lowest pKa will be the most acidic. In the other way, the conjugate base which the acid is weakest will be strongest.  

The weak base with the lowest pKb will be the most basic. And the conjugate base of the weakest base will be a strongest acid.

Using the values:

Ka HCN = 4.9x10⁻¹⁰

Kb HONH2 = 1.1x10⁻⁸

Ka HClA 3.0x10⁻⁸

Kb C2H5NH2 = 6.4x10⁻⁴

The NaNO3 is the conjugate base of a strong acid as HNO3. That means its solutions are almost neutral

The HONH3Br is the conjugate acid of a weak base. Its solutions will be acidics

C2H5NH3Cl is the conjugate acid of a weak base as ethylamine, its solutions will be acidic.

As ethylamine has a lower pkb than hydroxylamine, the conjugate acid of hydroxylamine will be more acidic.

NaF is the conjugate base of a weak acid as HF. Its solutions will be basics

The order in increasing pH is:

HONH3Br < C2H5NH3Cl < NaNO3 < NaF

Answer: element 68 is Erbium, should there be a picture attached?

Explanation:

Answer:  dispersion forces, dipole-dipole and hydrogen bonds

Explanation: