The human eye is able to detect as little as 2.35 × 10–18 j of green light of wavelength 510 nm. Calculate the minimum number of photons of green light that can be detected by the human eye. Physical constants can be found here.

Answer: i really       dont know srry

Explanation:

The value of q when e = 0 at the given temperature in the question is :

Q =  1.3 * 10⁻²⁶

Given that

E = 0,  ΔG = -nFE,

therefore ΔG = 0

Also

Given that

ΔG = ΔG° + RTIn q

ΔG° = -  RTIn q

Hence ; Q = e^ (nFE°cell / RT) -- ( 1 )

where : n = 2, F = 96500, E°cell = -0.87 volt, R = 8.314, T = 339 k

insert  values into equation ( 1 )

Q =  1.3 * 10⁻²⁶

Note :  E°cell = reduction half reaction + oxidation half reaction

          = 0.20 volt - 1.07 volt  = -0.87 volt.

Hence we can conclude that The value of q when e = 0 at the given temperature in the question is : Q =  1.3 * 10⁻²⁶

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Answer:

Explanation:

Water molecule is H₂O, which means that there is one oxygen atom per each water molecule.

The balanced chemical equation that represents this is:

The stoichiometric coefficents 1 for O₂ (g) and 2 for H₂O (g) means that two molecules of oxygen are required to produce two molecules of water.

STP stands for standard temperature and pressure. Those conditions are 273.15 K (0 °C, 32 °F) and 100 KPa of absolute pressure.

That means that the reaction is carried out at constant temperature and pressure.

Then, since the  ideal gas law states that the at constant pressure and temperature the volume occupied by the gases is proportional to the number of particles (atoms or molecules), the molecular stoichiometric ratio of 1 molecule of O₂ (g) to 2 molecules for H₂O (g) is equivalent to the volumetric ratio 1 liter of O₂ to 2 liters of H₂O:

Hence, you conclude that 1 liter of oxygen is required to produce 2 liters of water, at STP.

Alpha particles are respective to the helium-4 ion. Therefore it has a mass of four and a positive charge of two. The correct answer is the mass number increases by 4.

If a nucleus emits an alpha particle, the mass number decreases by 4

An alpha particle is essentially identical to a helium nucleus. An alpha particle has a mass of four units and a positive charge of two units just as the helium nucleus.

Hence, if a nucleus emits an alpha particle, the mass number decreases by 4 while the atomic number decreases by two.

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In the reaction N2 + 3 H2 → 2 NH3, each nitrogen atom is reduced from 0 to -3, and each hydrogen atom is oxidized from 0 to +1. This is an oxidation-reduction reaction where nitrogen gains electrons (reduction), and hydrogen loses electrons (oxidation).

The correct statement for the provided reaction N2 + 3 H2 → 2 NH3 is: 'Each N atom is reduced from 0 to -3. Each H atom is oxidized from 0 to +1.' This reaction is an oxidation-reduction reaction, wherein the nitrogen atom is reduced (its oxidation number decreases from 0 to -3), and each hydrogen atom is oxidized (its oxidation number increases from 0 to +1).

In the process, nitrogen is gaining electrons, thus being reduced. On the other hand, hydrogen is losing electrons, thus being oxidized. This principle is aligned with the redox reactions wherein one element loses electrons (oxidation) and another element gains electrons (reduction). The reaction equation also follows the law of conservation of mass stating that matter cannot be created or destroyed.

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Answer:

[tex]\boxed{\text{18.2 kJ}}[/tex]

Explanation:

The formula for the heat involved is  

[tex]q = m\Delta_{\text{f}}\text{H}[/tex]

Data:

m = 115 g

[tex]\Delta_{\text{f}}\text{H} = \text{158.3 J/g}[/tex]

Calculation:

[tex]q = \text{115 g} \times \dfrac{\text{158.3 J}}{\text{1 g}}\\\\q = \text{18 200 J} = \textbf{18.2 kJ}}\\\\\text{It takes }\boxed{\textbf{18.2 kJ}} \text{ to melt the p-xylene}[/tex]

Answer:

C

Explanation:

Answer:

D

Explanation:measurement of heat The usual means of measuring temperature is a thermometer. It measures the degree or intensity of heat and usually consists of a glass tube with a bulb at the lower portion of the tube that contains mercury, colored alcohol, or a volatile liquid.

A the nucleus emits partials and or energy

It is an ester functional group

Answer:

1. Percentage composition O in CO₂ is 72.7%

2.Percentage composition of O in N₂O₅ is 74.1%

Explanation:

How to calculate percentage composition

I. Calculate the molar mass of the compound by summing up the atomic masses of the elements that makes up the compound

II. The percentage composition of the element is derieved by dividing the atomic mass of the atoms by the molar mass of the compound

III. Now express this ratio as a percentage.

1. Percentage composition of Oxygen in CO₂:

Molar mass of CO₂

Atomic mass of C = 12gmol⁻¹

Atomic mass of O = 16gmol⁻¹

Note: We have two atoms of Oxygen

Molar mass = [12 + (2x16)]gmol⁻¹

= (12 + 32)gmol⁻¹

= 44gmol⁻¹

Percentage composition O in CO₂

= (2x16)/44 x 100

= 32/44 x 100

= 0.727 x 100

= 72.7%

Percentage composition O in CO₂ is 72.7%

2. The percentage composition of O in N₂O₅

Atomic mass of N = 14gmol⁻¹

Atomic mass of O = 16gmol⁻¹

Molar mass of N₂O₅ = [(2x14) + (5x16)]gmol⁻¹

= (28 + 80)gmol⁻¹

= 108gmol⁻¹

Percentage composition of O in N₂O₅

= (5x16)/108 x 100

= 80/108 x 100

= 0.741 x 100

= 74.1%

Percentage composition of O in N₂O₅ is 74.1%

Note: Percentage composition is expressed as a percentage.

Final answer:

The percent composition of oxygen in CO2 is approximately 72.7%, and in dinitrogen pentoxide, it is approximately 74.1%. This is calculated by dividing the mass of oxygen in each molecule by the total molar mass of the molecule and then multiplying by 100%.

Explanation:

Percent Composition of Oxygen in Compounds

The percent composition of an element in a compound represents the mass percentage of that element in the total mass of the compound. To calculate the percent composition of oxygen in CO2 (carbon dioxide) and dinitrogen pentoxide, we need to look at the molar masses of these compounds and the elements within them.

CO2:

Carbon dioxide is composed of one carbon atom and two oxygen atoms. The molar mass of carbon is 12.01 g/mol and oxygen is 16.00 g/mol. Hence, the molar mass of CO2 equals 44.01 g/mol (12.01 + (16.00 × 2)). The mass of oxygen in CO2 is 32.00 g/mol, which we get from (16.00 × 2). To find the percent composition of oxygen in CO2, we divide the mass of oxygen by the molar mass of CO2 and multiply by 100%.

Percent composition of O in CO2 = (32.00 g/mol / 44.01 g/mol) × 100% ≈ 72.7%

Dinitrogen Pentoxide:

Dinitrogen pentoxide consists of two nitrogen atoms and five oxygen atoms. To calculate the percent composition of oxygen, we first find the molar mass of N2O5, which is 108.01 g/mol (14.01 × 2 + 16.00 × 5). The mass of oxygen in N2O5 is 80.00 g/mol, from (16.00 × 5). The percent composition of oxygen is then calculated as follows:

Percent composition of O in N2O5 = (80.00 g/mol / 108.01 g/mol) × 100% ≈ 74.1%

Answer:

0.643 mol.

Explanation:

where, P is the pressure of the gas in atm (P = 4.0 atm).  

V is the volume of the gas in L (V = 4000 mL = 4.0 L).  

n is the no. of moles of the gas in mol (n = ??? mol).

R is the general gas constant (R = 0.0821 L.atm/mol.K),  

T is the temperature of the gas in K (T = 30ºC + 273 = 303 K).

∴ n = PV/RT = (4.0 atm)(4.0 L)/(0.0821 L.atm/mol.K)(303 K) = 0.643 mol.

Answer:-

Name of Chemical Compound: (if given otherwise not necessary) Ethane.

Chemical formula: C2H6.

Finding molar mass of Ethane(C2H6):-

Molar mass of Ethane = 12×2+1×6

Molar mass of Ethane = 2 + 6

Molar mass of Ethane = 30 g/mol

[ Note:

• Molar mass: Mass(is represented/taken in grams)of one mole of a substance.

• g/mol means grams per mole ].

Answer:

Molar mass of ethane is determined by adding atomic mass of all the constituent atoms.

Explanation:

Molar mass of a molecule is determined by adding all the atomic masses of constituent atoms.

In ethane molecule, there are two carbon atoms and six hydrogen atoms.

Atomic mass of carbon is 12g and atomic mass of hydrogen is 1g.

So molar mass of ethane is- [tex](2\times atomic mass of C)+(6\times atomic mass of H)[/tex] or [tex](2\times 12g)+(6\times 1g)[/tex] or 30g.

Limiting reactant is the answer

Answer:

64 000 C; 71 min

Explanation:

1. Number of coulombs

a. Write the equation for the half-reaction.

Ca²⁺ + 2e⁻ ⟶ Ca

b. Calculate the moles of Ca

Moles of Ca = 13.3 g Ca × (1 mol Ca/40.08 g Ca) = 0.3318 mol Ca

c. Calculate the moles of electrons

Moles of electrons = 0.3318 mol Ca × (2 mol electrons/1 mol Ca) = 0.6637 mol electrons

d. Calculate the number of coulombs

No. of coulombs = 0.6637 mol electrons × (96 485 C/1 mol electrons)

= 64 000 C

It takes 64 000 C to produce 13.3 g of Ca.

2. Time required

Q  = It  

t = Q/I = 64 000 C/15 C·s⁻¹ = 4270 s

t = 4270 s × 1 min/60 s = 71 min

The process will take 71 min.

Answer:

Explanation:

Stoichiometry is the cuantitative study of the chemical reactions.

It is like algebra applied to chemical equations.

The cuantitative relations between the amount of reactants and products is determined by the law of conservation of mass: the number of each kind of atoms in the reactants must equal the number of the same kind of atoms in the products.

Once that relation has been established, as mole ratios, then it can be determined the amount of reactant neeed to obtain a certain amount of product, or vice versa, determine the amount of product that can be obtained from a given amount of reactants.

That is why, after you know the reactants and products in a chemical equation you must balance to assure that the relative amounts are properly established.

Final answer:

The first step in most stoichiometry problems is to plan the problem by writing and balancing the chemical equation correctly, which is foundational for accurate stoichiometry calculations.

Explanation:

The first step in most stoichiometry problems is to plan the problem. This typically involves writing and balancing the chemical equation. Ensuring that all formulas are correct and balanced is crucial as it lays the foundation for all subsequent calculations in the stoichiometry process. Once the equation is balanced, you can proceed to write the ionic and net ionic equations if necessary, assign oxidation numbers, or derive stoichiometric factors to relate the amounts of substances involved. It is also important to identify the 'given' information and what the problem is asking you to 'find,' as well as list other known quantities.

Answer:

Option C) 1,230 kJ

Explanation:

According to the data, 1 mol of propane liberates 2,220 kJ of energy when it is combusted. If we have 24.5 g of propane, this mass is equal to 0,56 mol (of propane):

44.097 g of propane---->1 mol

24.5 g of propane-------x= 0.56 mol

Then, the enthalpy of the described chemical reaction (propane´s combustion) is 2,220 kJ when 1 mol of propane is combusted, so:

1 mol propane---------->2,220 kJ of energy

0.56 mol propane (24.5 g)------------x= aproximately 1,24 kJ (which would be option C)

To calculate the enthalpy of combustion for 24.5g propane, divide the mass by the molecular weight to obtain the number of moles. Then, multiply the moles by the given enthalpy of reaction to find the enthalpy of combustion. The enthalpy of combustion for 24.5g propane is 1,230 kJ.

To calculate the enthalpy of combustion for 24.5g propane, we need to first convert the mass of propane to moles. Dividing the mass by the molecular weight of propane gives us 24.5 g / 44.097 g/mol = 0.5558 mol. Then, we can use the equation given to calculate the enthalpy of combustion:

Enthalpy of combustion = ΔHreaction * moles of propane

Plugging in the values, we get:
Enthalpy of combustion = 2,220 kJ/mol * 0.5558 mol = 1,230 kJ

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Answer:

Much younger than Earth

Explanation:

The moon is believed to be much more younger than the earth.

The moon is earth's only natural satellite.

It is hypothesised that a planetary body as big as Mars collided with earth. The impact causes vapourization and hauling of materials from the earth crust and mantle.

The blasted particles and the matter were pulled together by gravity. These ones formed our satellite, the moon.

Some of the matter fell back to the earth surface.

The moon was formed after earth was formed and it is much younger than our blue planet.

The Moon is about the same age as Earth, approximately 4.5 billion years old, with lunar rock samples dating between 3.3 and 4.4 billion years, indicating a shared origin in the solar system.

The age of the Moon is a subject of geologic interest and has been determined through scientific investigation, particularly through the analysis of lunar rocks retrieved during the Apollo missions. Studies have revealed that the Moon and Earth have approximately the same age, which is in the vicinity of 4.5 billion years old. Radiometric age-dating of the lunar rocks has shown that the samples solidified between about 3.3 and 4.4 billion years ago, which are substantially older than most of the rocks found on Earth.

Therefore, when answering the student's question about the Moon's age, the best choice is 'about the same age as Earth'. While there are lunar rocks that are older than most of Earth's rocks, both Earth and Moon formed together in the same time frame, in the earlier days of the solar system.

Answer:-

When the reaction takes place Ca is reduced or is an oxidizing agent.

Reaction:

Ca + 2Cl =CaCl2

Note: There is a +2 charge on Ca(Calcium) and -1 charge on each Cl-atom(Chlorine atom) hence the charges are cancelled. Therefore, the total charge on the whole compound is zero.

Explanation:-

• Reduction: gain of electron/electrons

gain of hydrogen

loss of oxygen

Oxidation: gain of oxygen

loss of hydrogen

loss of electron/electrons.

• Oxidizing agent/reduced

Reducing agent/oxidized

• The molecule that is oxidized loses an electron and the molecule that is reduced gains the electron that was lost by the oxidized molecule.

Answer:

[tex]\boxed{\text{Chlorine}}[/tex]

Explanation:

We must use oxidation numbers to decide which substance is reduced.  

[tex]\rm \stackrel{\hbox{0}}{\hbox{Ca}} + \stackrel{\hbox{0}}{\hbox{ Cl}_{2} }\longrightarrow \stackrel{\hbox{+2}}{\hbox{Ca }}\stackrel{\hbox{-1}}{\hbox{Cl}_{2}}[/tex]

The oxidation number of Ca increases from 0 in Ca to +2 in CaCl₂.

The oxidation number of Cl decreases from 0 in Cl₂ to -1 in CaCl₂.

[tex]\text{A decrease in oxidation number is reduction, so } \boxed{\textbf{Cl$_{2}$ is the substance reduced.}}[/tex]

Answer:

Explanation:

The innermost electron shell is the lowest principal energy level, i.e n = 1.

For n = 1 there is only one orbital, the 1s orbital.

As stated by the Pauli's exculsion principle an orbital may have a maximum of two electrons, and they have opposed spins.

Then, the innermost electron shell has just one orbital and, in consequence, can hold up to 2 elecrons.

The innermost electron shell of an atom can hold up to two electrons.

The innermost electron shell of an atom, also known as the first shell or K-shell, can indeed hold a maximum of 2 electrons. This is often based on the quantum mechanical model of the atom, where the electrons are organized into various shells and subshells.

In addition to this, the first shell consists of only one subshell, called the 1s subshell, which accommodates a maximum of 2 electrons. The distribution of electrons in shells and subshells is a fundamental aspect of atomic structure and determines the chemical properties of elements, as well as their interactions in chemical reactions and bonding.

Answer:

KIKOKEN

Explanation:

(1/2)^3 is the fraction of a sample after 3 half lives

The boiling point of a 0.1 mole glucose in 200 ml water solution is approximately 100.255°C at 1 atm, after calculating the molality as 0.5 m and applying the molal boiling point elevation constant for water of 0.51°C/m.

The question asks: What is the boiling point of a solution of .1 mole of glucose in 200 ml of water? To calculate this, we need to first determine the molality (m) of the glucose solution since we have the molal boiling point elevation constant (Kb) for water, which is 0.51°C/m.

The molality (m) is calculated by the number of moles of solute per kilogram of solvent (water in this case). Given that 0.1 mole of glucose is dissolved in 200 ml (or 0.2 kg) of water, the solution's molality would be 0.5 m (0.1 mole / 0.2 kg). Since the constant Kb is 0.51°C/m, the boiling point elevation would be 0.5 m x 0.51°C/m = 0.255°C.

The normal boiling point of water is 100°C at 1 atm. We add the boiling point elevation to this to get the boiling point of the glucose solution: 100°C + 0.255°C = 100.255°C. Therefore, the boiling point of the given glucose solution would be approximately 100.255°C at 1 atm.

A water molecule consists of two hydrogen atoms bonded to an oxygen atom, and its overall structureis bent. This is because the oxygen atom, in addition to forming bonds with the hydrogen atoms, also carries two pairs of unshared electrons.

Answer:

Explanation:

The structure of water molecule is very simple . it's has a central oxygen atom ( which has a valency of two ) . Since it's valency is two , it can two hydrogen atoms to both of it's sides ( which have a valency of one )

Structure :

H-O-H

Water is known as amphoteric substance , as it has the ability to act as either a base or an acid ( depending upon the substance it's reacting with ) . On top of that a very electro negative oxygen atom reacts with an electro positive hydrogen gives the molecule a strong bonding force ( which results in a molecule that is held by hydrogen bonding , which is a very strong attraction) . And when its bonded with some strong electro forces of attraction , Guess what happens ? It's boiling point increases !!!! ( It means you have to heat it up more to boil water ) . Which also means it has high heat of vaporization ( to get water into it's vapour state ) .all of that just because it has high forces if attraction between one another ...

Answer:

[tex]\boxed{\text{2.00 mol}}[/tex]

Explanation:

We know we will need a balanced chemical equation with masses and molar masses, so, let's gather all the information in one place.

You don't tell us what the reaction is, but we can solve the problem so long as we balance the OH.

M_r:      58.32

          Mg(OH)₂ + … ⟶ … + 2HOH

m/g:       58.3

(a) Moles of Mg(OH)₂

[tex]\text{Moles of Mg(OH)$_{2}$} =\text{58.3 g Mg(OH)$_{2}$} \times \dfrac{\text{1 mol Mg(OH)$_{2}$}}{\text{58.32 g Mg(OH)$_{2}$}}\\\\=\text{0.9997 mol Mg(OH)$_{2}$}[/tex]

(b) Moles of H₂O

The molar ratio is 2 mol H₂O = 1 mol Mg(OH)₂.

[tex]\text{Moles of H$_{2}$O}= \text{0.9995 mol Mg(OH)$_{2}$} \times \dfrac{\text{2 mol {H$_{2}$O}}}{ \text{1 mol Mg(OH)$_{2}$}}\\\\= \textbf{2.00 mol H$_{2}$O}[/tex]

The reaction will form [tex]\boxed{\textbf{2.00 mol}}[/tex] of water.

When 58.3 grams of magnesium hydroxide react, it forms 2 moles of water. This is determined through the conversion of grams to moles and using the stoichiometry of the reaction.

To find out how many moles of water would form the reaction of exactly 58.3 grams of magnesium hydroxide, we need to convert grams of Mg(OH)2 to moles and then use stoichiometry to find out the number of moles of H2O produced.

The molecular weight of Mg(OH)2 is 58.3197 g/mol. Therefore, the number of moles of Mg(OH)2 is given by:

Mass (g) / Molecular weight (g/mol) = 58.3g / 58.3197g/mol = 1 mole Mg(OH)₂

According to the reaction Mg(OH)2 -> Mg²⁺ + 2OH⁻, 1 mole of magnesium hydroxide decomposes to form 1 mole of magnesium ions and 2 moles of hydroxide ions. Therefore, 1 mole of Mg(OH)₂ reacts to form 2 moles of water.

So, 1 mole of Mg(OH)2 would result in the formation of 2 moles of water. Hence, 58.3 grams (which correspond to 1 mole) of Mg(OH)2 would form 2 moles of water.

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Answer:

Produces energy that are useful in nuclear power plants

Explanation:

Nuclear fission is a the radioactive disintegration of a heavy nucleus into simpler ones. The fission process which initiates a chain reaction releases a lot of neutrons and a large amount of energy.

The energy released in a fission process is very useful in nuclear power plants for producing electricity.

Answer:

CoCl₃ > Li₂SO₄ > NH₄I.

Explanation:

ΔTf = i.Kf.m,

where, ΔTf is the depression in freezing point.

i is the van 't Hoff factor.

Kf is the molal depression constant of water.

m is the molality of the solution.

(1) Li₂SO₄:

i for Li₂SO₄ = no. of particles produced when the substance is dissolved/no. of original particle = 3/1 = 3.

∴ ΔTb for (Li₂SO₄) = i.Kb.m = (3)(Kf)(m) = 3(Kf)(m).

(2) NH₄I:

i for NH₄I = no. of particles produced when the substance is dissolved/no. of original particle = 2/1 = 2.

∴ ΔTb for (NH₄I) = i.Kb.m = (2)(Kf)(m) = 2(Kf)(m).

(3) CoCl₃:

i for CoCl₃ = no. of particles produced when the substance is dissolved/no. of original particle = 4/1 = 4.

∴ ΔTb for (CoCl₃) = i.Kb.m = (4)(Kf)(m) = 4(Kf)(m).

CoCl₃ > Li₂SO₄ > NH₄I.

These are two questions and two complete answers.

Answers:

Explanation:

A) Question #5.

The figure shows that the parent nuclide is [tex]^{222}_{86}Ra[/tex] and the daughter nuclide is [tex]^{218}_{84}Po[/tex]

A mass number balance and an atomic number balance show the features of the radiation emitted.

a) Mass number balance:

The mass number is the superscript to the left of the chemical symbol and is the amount of protons and neutrons in the nucleus of the atom.

Hence, the mass number of the unknown emitted particle is 4.

b) Atomic number balance.

The atomic number is the subscript to the left of the chemical symbol and is the number of protons in the nucleus of the atom.

Hence, the atomic number (number of protons) of the unknown emitted particle is 2.

Conclusion: the emitted particle is a particle with 2 protons and 2 neutrons, which is a nucleus of helium, ⁴₂He, also called alpha particle, and the reaction is named alpha decay.

B) Question #6

Again, a mass number balance and an atomic number balance will tell which element is the missing product in the reaction.

The reaction is:

[tex]^{233}_{92}U+^1_0n{->}^{99}_{42}Mo+3^1_0n+?[/tex]

a) Atomic number balance:

Hence, the missing product has atomic number 50 which permits to tell that it is an atom of tin (Sn).

b) Mass number balance:

Which means that the missing product has a 132 neutrons and protons:

The symbol of this atom is:

Answer:

2.

Explanation:

2Al(s) + 3FeCl₂(aq) → 2AlCl₃(aq) + 3Fe(s).

It is clear that 2 mol of Al react with 3 mol of FeCl₂ to produce 2 mol of AlCl₃ and 3 mol of Fe.

The stoichiometric coefficient for aluminum, Al when the chemical equation is balanced is 2.

To obtain the stoichiometric coefficient for aluminum, we shall write and balance the equation for the reaction. This is illustrated below:

Aluminum => Al

Iron (II) chloride => FeCl₂

Aluminum chloride => AlCl₃

Iron => Fe

Aluminum + Iron (II) chloride —> Aluminum chloride + Iron

Al + FeCl₂ –> AlCl₃ + Fe

There are 3 atoms of Cl on the right side and 2 atoms on the left side. It can be balance by writing 3 before FeCl₂ and 2 before AlCl₃ as shown below:

Al + 3FeCl₂ –> 2AlCl₃ + Fe

There are 2 atoms of Al on the right side and 1 atom on the left. It can be balance by writing 2 before Al as shown below:

2Al + 3FeCl₂ –> 2AlCl₃ + Fe

There are 3 atoms of Fe on the left side and 1 atom on the right side. It can be balance by writing 3 before Fe as shown below:

2Al + 3FeCl₂ –> 2AlCl₃ + 3Fe

Now, the equation is balanced.

The coefficient of Aluminum, Al in the balanced equation is 2.

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Answer:

2.2 J/°C.g.

Explanation:

Q = m.c.ΔT,

where, Q is the amount of heat released by the unknown substance (Q = 550 J).

m is the mass of the unknown mass (m = 25.0 g).

c is the specific heat of the unknown substance (c = ??? J/°C.g).

ΔT is the difference between the initial and final temperature (ΔT = 10°C).

∴ c = Q/(m.ΔT) = (550 J)/(25.0 g)(10°C) = 2.2 J/°C.g.