what is the difference between the number of electrons in an atom of selenium, Se and the number of electrons in an atom of aluminum, Al?

Answer:

C. Physical Change

Explanation:

Peeling a banana is not changing the banana's structure, it's still the same banana, but it looks different, which is a chemical change! Hope I helped!

Answer:

32.4%

Explanation:

%Yield = Actual Yield/Theoretical Yield x 100% = (12.7/39.2)100% = 32.4%

Answer:

number of protons is more than the number of electrons.

Explanation:

A cation is a positively charged ion.

An ion is an atom that has lost or gained electron(s). In an ion, the number of protons and electrons are not the same.

Number of protons is the number of positively charged particles

Number of electrons is the number of negatively charged particles.

 For a cation, which is positively charged, the number of protons is more than the number of electrons.

Therefore, in cations, we have more protons than electrons.

Answer:

577.6 mmHg

Explanation:

What is the conversion between atm (standard atmosphere) and mmHg (millimeters of mercury)?

Multiply the atm amount by 760 to get the mmHg amount.

19/25 * 760/1

19/5 * 152/1

(19*152)/5

2888/5

577 3/5 or 577.6 mmHg

Answer:

Establish and Use a Secure Connection

Use SSH Keys Authentication

Secure File Transfer Protocol

Secure Sockets Layer Certificates

Use Private Networks and VPNs

Explanation:

Answer:

Taste comes from the stimulation of chemical receptors in nerve cells on the tongue by particular chemical structures of substances. If there are no chemical structures pertaining to any of the chemical sensors, the substance would appear to be tasteless. All of these chemicals interact with the sensors with the help of the medium of saliva which has a lot of water. For example: the salt sensors might be susceptible to ions and the sweet sensors might be susceptible to hydroxyl groups on the sugars.

Now, taste is not a very precise field of study. A same substance may taste subtly different to different people. Can we be sure that water has no taste? The chemical sensors are always exposed to water. It might be that there are no sensors for water. It might also be that the signal for water is negated as a background signal. If water did have a particular taste, one thing is for certain, we would be tasting water in every bite of food and even at times when we are not eating as we always have saliva in your mouth.

Hope this helps, have a wonderful day/night, and stay safe!

The number of atoms in 1 mole of carbon equals the number of atoms in 1 mole of boron is false because the molar mass of carbon is different from that of boron. Option A is correct.

From the listed option the number of atoms in 1 mole of carbon equals the number of atoms in 1 mole of boron is false because the molar mass of carbon is different from that of boron

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Answer:

0.089

Explanation:

2.5/ 14= .178 then 0.178/ 2 again and you get 0.089

The moles of nitrogen in 2.5 grams of the compound is 0.089 moles. Thus option A is correct.

Moles can be calculated as the ratio of mass to molecular mass.

Moles = [tex]\rm \dfrac{weight}{molecular\;weight}[/tex]

The mass of Nitrogen = 14 g/mol

The mass of diatomic nitrogen = 2 [tex]\times[/tex] mass of nitrogen

The mass of diatomic nitrogen = 2 [tex]\times[/tex] 14 g/mol

The mass of diatomic nitogen = 28 g/mol

The molecular weight of Nitrogen = 28g/mol

Given, the mass of Nitrogen = 2.5 g

Moles of nitrogen = [tex]\rm \dfrac{2.5}{28}[/tex]

Moles of Nitrogen = 0.089 moles.

The moles of nitrogen in 2.5 grams of the compound is 0.089 moles. Thus option A is correct.

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Explanation:

A physical change is a change that alters the physical properties of matter particularly the form and state.

In many cases the change is easily reversible. Examples are changes of state such as freezing, boiling, melting e.t.c

A chemical change is a change in which a new kind of matter is formed. It is always accompanied by energy changes which can either be evolution or absorption of heat or light or both.

The process is not easily reversible. Examples are combustion, rusting of iron, precipitation, e.t.c

During a chemical reaction, the reactants undergo a chemical change.

Answer: a) [tex]Cu\rightarrow Cu^{2+}+2e^-[/tex]  : anode

b. [tex]2H^++2e^-\rightarrow H_2[/tex] : cathode

c. [tex]O^{2-}\rightarrow \frac{1}{2}O_2+2e^-[/tex]:  anode

Explanation:

Electrochemical cell is a device which converts chemical energy into electrical energy. It consist of two electrodes, anode and cathode.

Oxidation i.e. loss of electrons , which results in an increase in oxidation number occurs over anode.

Reduction i.e. gain of electrons, which results in decrease in oxidation number occurs over cathode.

a. [tex]Cu\rightarrow Cu^{2+}+2e^-[/tex]  : oxidation :  anode

b. [tex]2H^++2e^-\rightarrow H_2[/tex] : reduction : cathode

c. [tex]O^{2-}\rightarrow \frac{1}{2}O_2+2e^-[/tex]: oxidation : anode

Answer:

A Variac or Powermite; gradually; 50-60%.

Explanation:

A chemical reaction can be defined as a chemical process which typically involves the transformation or rearrangement of the atomic, ionic or molecular structure of an element through the breakdown and formation of chemical bonds to produce a new compound or substance.

Some of the laboratory apparatus (equipment) used for conducting a chemical reaction are conical flask, Bunsen burner, beaker, tongs, crucible, round bottom flask etc.

In order to heat a round bottom flask in a heating mantle, plug the heating mantle into a Variac or Powermite which is typically used for controlling the level of temperature. Turn the heat up gradually, and do not exceed 50-60% of the maximum output of the device, so as to avoid any electrical issues such as overloading, short-circuit etc.

The safety precautions that must be taken when using a round bottom flask are;

I. A proper inspection of the round bottom flask for cracks, irregularities or any imperfection.

II. Ensure you avoid heating the flask while it is closed.

III. When suspending the round bottom flask on a stand, you should ensure that you use a clamp for stability.

Answer:

It does not change the identity of a substance. Sugar if dissolved in water is still sugar.

Explanation:

Answer:0

Explanation:

Answer:

Chemical formula of the compound = K₂O

Explanation:

Given:

Number of potassium cation = 2

Number of oxygen anion = 1

Cross valency

Symbol of potassium = k

Symbol of oxygen = o

So;

Chemical formula of the compound = K₂O

4-,3-,2-,1-,0,1,2,3,4

Answer:

Pressure = 0.62 atm

Explanation:

[tex]V_{1}[/tex] = 85 [tex]cm^{3}[/tex], [tex]P_{1}[/tex] = 1.45 atm,  [tex]T_{1}[/tex] = 310 K, [tex]V_{2}[/tex] = 180 [tex]cm^{3}[/tex], [tex]T_{2}[/tex] = 280 K.

Applying the general gas law,

[tex]\frac{P_{1} V_{1} }{T_{1} }[/tex] = [tex]\frac{P_{2} V_{2} }{T_{2} }[/tex]

[tex]\frac{1.45*85}{310}[/tex] = [tex]\frac{P_{2}*180 }{280}[/tex]

[tex]P_{2}[/tex] = [tex]\frac{1.45*85*280}{180*310}[/tex]

   = [tex]\frac{34510}{55800}[/tex]

   = 0.62

[tex]P_{2}[/tex]  = 0.62 atm

The pressure when the volume is increased and the temperature reduced to the given values is 0.62 atm.

that is the correct answer don't worry :))

Answer:

*helps*

Explanation:

Answer:

D

Explanation:

I hope this helps and have a great day

Answer: 720 g

Explanation:

To solve this we must be knowing each and every concept related to mole. Therefore, shivani measures out 6.0 moles of epsom salt (MgSO[tex]_4[/tex]) to put her bath. 1,566g MgSO[tex]_4[/tex] went in the bath.

A mole is merely a measuring unit. In reality, it is one of its International System of Units' seven foundation units. When current units are insufficient, new units are created.

Chemical reactions frequently occur at levels where employing grams would be inappropriate, but using absolute quantities of atoms/molecules/ions would also be misleading.

For all practical reasons, one mole of a substance in grams is nearly equal to 1 molecule for the compound per daltons.

Mathematically,

number of mole =given mass ÷ molar mass

number of mole=6.0 moles

molar mass of epsom= 261.47g/mol

substituting all the given values in the above equation, we get

6.0 moles =mass of epsom ÷ 261.47g/mol

mass of epsom =1,566g

Therefore, 1,566g  MgSO[tex]_4[/tex] went in the bath.

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Answer:

double replacement

Explanation:

The reaction shown is a double replacement reaction.

It is also known as double decomposition or metathesis reaction.

In such a reaction, there is an actual exchange of partners to form new compounds.

One of the following is the driving force for such reaction:

Answer:

22.6%

Explanation:

I just answered and got it right

Answer:

B.  LiF < CH6N < H2O2 <I2

Explanation:

Find the molar mass of LiF

To do that, first look at the atomic mass of each element on the periodic table.

But they are one lithium atom and one fluorine atom

So you use this equation:

LiF has 25.9 g/mol

Now find the molar mass of CH6N.

To do that, first look at the atomic mass of each element on the periodic table.

But they are six hydrogen atoms, one carbon atom, and one nitrogen atom.

So you use this equation:

CH6N has 32 g/mol

Now find the molar mas of H2O2

To do that, first look at the atomic mass of each element on the periodic table.

But they are two oxygen atoms and two hydrogen atoms.

So you use this equation:

H2O2 has 34 g/mol.

Lastly, find the molar mass of I2

To do that, first look at the atomic mass of each element on the periodic table.

But they are two iodine atoms.

So you use this equation:

I2 has 253.8 g/mol

Now that we calculated the molar mass of all elements. We rank it in the following of increasing atomic mass.

Therefore, the final answer is B.  LiF < CH6N < H2O2 <I2

Hope it helped!

Answer:

Covalent bonding occurs when electrons are shared between atoms. Double and triple covalent bonds occur when four or six electrons are shared between two atoms, and they are indicated in Lewis structures by drawing two or three lines connecting one atom to another.

Explanation:

Answer: 12.2 moles

Explanation:

7.36x10^24/6.02214076x10^23 = 12.2 moles of free oxygen atoms

Answer:

6.5256×10¹⁴

Explanation:

n= v/24

v= n×25

v= 2.719×10¹³ × 24= 6.5256×10¹⁴ moles/dm³

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According to ideal gas equation, the volume occupied by 2.719 x 10¹³ moles of methane gas is 6174.76×10¹³cm³.

The ideal gas equation is a equation which is applicable in a hypothetical state of an ideal gas.It is a combination of Boyle's law, Charle's law,Avogadro's law and Gay-Lussac's law . It is given as, PV=nRT where R= gas constant whose value is 8.314.The law has several limitations.Ideal gases exist in hypothetical state.The law was proposed by Benoite Paul Emile Clapeyron in 1834.

Substituting values of pressure=1 atmosphere,number of moles=2.719 x 10¹³ ,R=8.314 ,T=273.15 K.

Therefore volume=nRT/P=2.719x 10¹³×8.314×273.15/1=6174.76×10¹³ cm³.

Thus, the volume occupied by 2.719 x 10¹³ moles of methane gas is 6174.76×10¹³cm³.

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Answer:

it will A. d. e. f option above

Considering the solution of mole fraction, molality and molarity, you obtain that:

(a) the mole fraction of thiophene in the solution is 0.039.

(b) the molality of thiophene in the solution 0.4429 [tex]\frac{moles}{kg}[/tex].

(c)  the molarity of thiophene in the solution is 0.373[tex]\frac{moles}{L}[/tex].

You know that:

The molar fraction is a way of measuring the concentration that expresses the proportion in which a substance is found with respect to the total moles of the solution.

Being the molar mass of each compound equals to:

the number of moles of each compound can be calculated as:

The total moles is obtained from the addition of the moles of the solute (C₄H₄S) and the solvent (C₇H₈):

total moles = moles C₄H₄S + moles C₇H₈ = 0.096 moles + 2.35 moles = 2.45 moles

Then, the mole fraction of thiophene in the solution can be calculated as:

[tex]mole fraction of thiophene=\frac{0.096 moles}{2.45 moles}[/tex]

Solving:

mole fraction of thiophene= 0.039

Finally, the mole fraction of thiophene in the solution is 0.039.

Molality is the ratio of the number of moles of any dissolved solute to kilograms of solvent.

The Molality of a solution is determined by the expression:

[tex]Molality=\frac{number of moles of solute}{kilograms of solvent}[/tex]

In this case, you know:

Replacing:

[tex]Molality C_{4} H_{4}S =\frac{0.096 moles}{0.21675 kg}[/tex]

molality C₄H₄S= 0.4429 [tex]\frac{moles}{kg}[/tex]

Finally, the molality of thiophene in the solution 0.4429 [tex]\frac{moles}{kg}[/tex].

Molarity is the number of moles of solute that are dissolved in a certain volume and is determined by the following expression:

[tex]Molarity=\frac{number of moles of solute}{volume}[/tex]

Assuming that the volumes of solute and solvent are additive, you can add the volume of C₄H₄S and C₇H₈.

But first, you need yo know the volume of C₄H₄S, which can be calculated from the mass and density:

[tex]Volume C_{4} H_{4}S =8.10 grams\frac{1 mL}{1.065 grams}[/tex]= 7.606 mL= 0.007606 L

Then, the total volume of the solution is calculated as:

total volume of the solution= volume C₇H₈ + volume C₄H₄S

total volume of the solution= 0.250 L + 0.007606 L = 0.257606 L

So, the molarity of thiophene in the solution can be calculated as:

[tex]Molarity C_{4} H_{4} S=\frac{number of moles of C_{4} H_{4} S}{totalvolumeof the solution}[/tex]

Replacing:

[tex]Molarity C_{4} H_{4} S=\frac{0.096 moles}{0.257606 L}[/tex]

Solving:

Molarity C₄H₄S= 0.373 [tex]\frac{moles}{L}[/tex]

Finally, the molarity of thiophene in the solution is 0.373[tex]\frac{moles}{L}[/tex].

In summary, you get:

(a) the mole fraction of thiophene in the solution is 0.039.

(b) the molality of thiophene in the solution 0.4429 [tex]\frac{moles}{kg}[/tex].

(c)  the molarity of thiophene in the solution is 0.373[tex]\frac{moles}{L}[/tex].

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