Brainly User
01/23/2022
Chemistry
High School
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Vinegar (acetic acid) and baking soda (sodium bicarbonate) react in an endothermic reaction to produce sodium acetate, carbon dioxide, and water. Which statement justifies classifying the reaction as endothermic?
A. The reaction produces water.
B. The bonds in both the reactants and products are covalent bonds.
C. The reaction needs a catalyst.
D. The total potential energy of the products is less than the total potential energy of the reactants.

The energy value to kilocalories (kcal) would be 32.5 kcal.

One kilogram of water requires one kilocalorie (1 kcal, or 1000 calories) of heat energy to raise its temperature by one degree Celsius (°C). Joule is the SI-standard unit for energy (J). About 4.18 calories make up one kcal.

The phrase used to describe how much energy is needed to raise a liter of water's temperature by one degree Celsius at sea level. The term "calorie" is frequently used in nutrition terminology to describe a unit of dietary energy.

Let the equation be

1 kJ = 1,000 J

1 cal = 4.184 J

1 kcal = 1,000 cal

136 kj x 1000j/1kj = 1.36 x [tex]$$10^5[/tex] J

simplifying the equation, we get

1.36 x [tex]$$10^5[/tex] J x 1 cal/4.184J = 32, 500

32500 cal x 1 kcal/1,000 cal = 32.5 kcal.

Therefore, the energy value to kilocalories (kcal) would be 32.5 kcal.

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The pH value of the water decreased: indicating that it became more acidic compared to the first test.

During the experiment, the student blew bubbles into the water, which introduced carbon dioxide. Carbon dioxide reacts with water to form carbonic acid, a weak acid that can lower the pH of the water. As a result: the pH value of the water decreased, indicating that it became more acidic.

This is because the concentration of hydrogen ions, which determine acidity, increased in the water. The change in pH value may have implications for the organisms living in the water, as different pH levels can affect their survival and growth. Therefore understanding the effects of human activities, such as blowing bubbles into water, on pH levels is important for maintaining the health of aquatic ecosystems.

This question should be given as:

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The molar solubility of CdF₂ in pure water is 0.0585M, and adding NaF decreases this solubility because the equilibrium shifts to favor the precipitation of some CdF₂. The correct option is A.

According to the statement, the option that identifies the molar solubility of CdF₂ in pure water and explains the effect that the addition of NaF has on this solubility is [CdF₂]eq = [Cd₂+]eq = 0.0585 M (since the solubility product expression for CdF₂ gives Ksp = [Cd₂+][F-]², and F- is in excess).

The molar solubility of CdF₂ in pure water can be determined by calculating the concentration of Cd₂+ and F− ions in the saturated solution, and then using the stoichiometry of the equilibrium reaction to determine the concentration of CdF₂ that would dissolve in pure water.

From the equilibrium equation: CdF₂(s) ⇄ Cd₂+(aq) + 2F−(aq), we know that for every mole of CdF₂ that dissolves, 1 mole of Cd₂+ and 2 moles of F− ions are produced.

The effect of adding NaF to the saturated solution can be explained by the common ion effect. When NaF is added, it provides additional F− ions, which are already present in the saturated solution, and thus increases the concentration of the common ion.

This leads to a shift in the equilibrium to the left, causing more CdF₂ to precipitate out of solution until a new equilibrium is established. As a result, the molar solubility of CdF₂ in the solution decreases.

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Complete question:

CdF₂(s)⇄Cd₂+(aq)+2F−(aq) A saturated aqueous solution of CdF₂ is prepared. The equilibrium in the solution is represented above. In the solution, [Cd₂+]eq=0.0585M and [F−]eq=0.117M. Some 0.90MNaF is added to the saturated solution. Which of the following identifies the molar solubility of CdF₂ in pure water and explains the effect that the addition of NaF has on this solubility?

a. The molar solubility of CdF₂ in pure water is 0.0585M, and adding NaF decreases this solubility because the equilibrium shifts to favor the precipitation of some CdF₂.

b. The molar solubility of CdF₂ in pure water is 0.0585M, and adding NaF has no effect on the solubility because only changes in temperature can increase or decrease the molar solubility of an ionic solid.

c.The molar solubility of CdF₂ in pure water is 0.117M, and adding NaF decreases this solubility because the equilibrium shifts to favor the precipitation of some CdF₂.

d. The molar solubility of CdF₂ in pure water is 0.176M, and adding NaF increases this solubility because the Na+ ions displace the Cd₂+ ions, causing the equilibrium to shift to favor the products.

An ionic compound comprised of Na+ and Cl is sodium chloride. An anion is a negative charges chlorine ion (Cl) and a cation is a positive sodium ion (Na+).

The sodium and chlorine ions exert an electric pull on one another when one sodium electron is transferred to a chlorine ion, binding the sodium and chlorine molecules together.

Because it attracts objects to itself from any distance, gravitational force is a very well-known example of attraction. More details regarding how this force operates are provided by Newton's global law of gravity.

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Based on the mass of 1 mole of nitrogen atoms, 7.55 x 10²³ atoms of nitrogen have a mass of 17.56 grams.

The number of atoms in 1 mole of nitrogen = 6.02 * 10²³ atoms

The mass of 1 mole of atoms of nitrogen = 14 g

Hence, 6.02 * 10²³ atoms has a mass of 14.01 g

Mass of 7.55 x 10²³ atoms = 14.01 g/mol * 7.55 x 10²³ / 6.02 * 10²³

The mass of 7.55 x 10²³ = 17.56 g

So,7.55 x 10²³ atoms of nitrogen have a mass of 17.56 grams.

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Acid is sour taste, corrosive and has lots of H+, while base is soapy and has lots of OH-. A pH is degree to measures how acid or base a solution is. The more H+ ions, the more acidic it is and the lower the pH will be. 

The terms acid and base describe chemical characteristics of the substances. The properties of acids are as follow :

For example : lemon, vinegar and others

While base (alkalies) has these properties :

For example : soap and many more

To measure the strength of the acids and bases, we can see from the pH scale. pH stands for potential or power of hydrogen. The pH scale is range from 0 to 14. Acids have a pH below 7, bases have a pH above 7 while pH 7 is said to be neutral.

Thus, the more H+ ions, the more acidic it is and the lower the pH will be. 

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Robert A. Millikan able to determine, either from his own work, The mass of an electron. Hence, the correct option is (c).

Robert A. Millikan was able to determine the charge of an electron, but the discovery of the electron itself was made by J.J. Thomson. Millikan's work built on Thomson's discovery and helped to refine our understanding of the properties of electrons. By conducting the oil drop experiment, Millikan was able to measure the charge of an electron with great precision. He observed the motion of tiny oil droplets that were suspended in an electric field, and by measuring the strength of the electric field and the speed of the droplets, he was able to calculate the charge of each droplet. By adjusting the strength of the electric field, he was able to find the smallest possible charge that a droplet could have, which corresponded to the charge of a single electron. However, Millikan did not determine the mass of an electron, as this was already known from Thomson's work on the charge-to-mass ratio of electrons. Additionally, Millikan did not propose a model of an atom with a small, positively charged nucleus, as this idea was developed later by Ernest Rutherford.

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ATP hydrolysis releases energy in the form of a high-energy phosphate bond.

This energy can be harnessed to drive energetically unfavorable condensation reactions, such as the reaction A-H + B-OH → A-B + H2O. In this reaction, a covalent bond is formed between A and B, while a water molecule is released.

The overall reaction can be written as:

B-OH + ATP → B-PO4 + ADP (phosphorylation of B)

B-PO4 + A-H → A-B + H2O + Pi (condensation reaction)

The overall reaction is exergonic, as it involves the release of energy from the hydrolysis of ATP, which is coupled to the energetically unfavorable condensation reaction.

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The tropical regions of earth contains the highest concentration of water vapor and higher altitudes and poles have the lower water vapor concentration.

Lower atmospheric water vapor molecules absorb heat generated from the Earth's surface. In turn, the water vapor molecules emit heat in all directions. The Earth's surface receives some of the heat back.

In the tropics, as the seasons change, a band of extremely humid air sways both north and south of the equator. The Intertropical Convergence Zone, where the easterly trade winds from either hemisphere meet and create almost daily thunderstorms and clouds, includes this ring of dampness.

Water vapor concentrations are higher farther from the equator in the summer-experienced hemisphere and lower in the winter-experienced one.

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the outcome of combining an alkyne with one equivalent of hcl is st -CEC-H + 1H-CI. 3-methyl-1-butyne 2-chloro-3-methyl-1-butene.

An alkyne is a type of hydrocarbon with a triple bond between two carbon atoms, which makes it unsaturated and more reactive than its corresponding alkane or alkene. Alkynes have the general formula CnH2n-2 and can have multiple triple bonds, giving rise to a range of isomers with different properties. Alkynes are used in many industrial processes, such as in the production of polymers, solvents, and pharmaceuticals, and are also important intermediates in organic synthesis. Alkynes can undergo various types of reactions, such as addition, substitution, and polymerization, and their reactivity can be modulated by the choice of substituents, reaction conditions, and catalysts. Alkynes are also of interest in the field of materials science, as they can form strong covalent bonds with metals and semiconductors, and can be used as building blocks for molecular electronics and nanotechnology.

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The number of moles in 2.3 grams of sodium atom is 0.1 moles and is calculated by formula, mass/molar mass.

Mole is defined as the unit of amount of substance . It is the quantity measure of amount of substance of how many elementary particles are present in a given substance.

It is defined as exactly 6.022×10²³ elementary entities. The elementary entity can be a molecule, atom ion depending on the type of substance. Amount of elementary entities in a mole is called as Avogadro's number.It is given as,mass/molar mass= 2.3/23=0.1 moles

Thus, there are 0.1 moles in 2.3 grams of sodium.

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Formaldehyde is a molecule with the chemical formula CH2O. It consists of a central carbon atom bonded to two hydrogen atoms and an oxygen atom, with a double bond between the carbon and oxygen atoms. The relative electronegativity values of the elements involved in formaldehyde are as follows:

• Carbon: 2.55

• Hydrogen: 2.20

• Oxygen: 3.44

Electronegativity is a measure of an atom's ability to attract the electrons towards itself in a covalent bond. In a covalent bond between two different atoms, the electrons are shared between them, but they may not be shared equally. In formaldehyde, the oxygen atom is more electronegative than the carbon atom. Therefore, the oxygen atom attracts the shared electrons in the double bond more strongly towards itself, resulting in a greater electron density around the oxygen atom. This creates a partial negative charge on the oxygen atom and a partial positive charge on the carbon atom. Similarly, the hydrogen atoms in formaldehyde have a lower electronegativity than the carbon atom. Therefore, the electrons in the C-H bonds are shared unequally, with a partial negative charge on the hydrogen atoms and a partial positive charge on the carbon atom.

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The chemical equation for the combustion of butane (C4H10) with excess oxygen (O2) is:

C4H10 + 13/2 O2 → 4 CO2 + 5 H2O

The balanced equation shows that 1 mole of butane reacts with 13/2 moles of O2 to produce 4 moles of CO2 and 5 moles of H2O. The change in energy for the combustion of butane can be calculated using bond enthalpies, which are given in units of kJ/mol of bonds broken or formed.

The bond enthalpies needed for this calculation are:

C-H = 413 kJ/mol

C-C = 348 kJ/mol

C=O = 799 kJ/mol

O=O = 498 kJ/mol

O-H = 463 kJ/mol

First, we need to calculate the total energy required to break the bonds in butane:

4 C-H bonds × 413 kJ/mol/bond = 1652 kJ/mol

8 C-C bonds × 348 kJ/mol/bond = 2784 kJ/mol

The total energy required to break the bonds in butane is:

1652 kJ/mol + 2784 kJ/mol = 4436 kJ/mol

Next, we need to calculate the total energy released by forming new bonds in the products:

8 C=O bonds × 799 kJ/mol/bond = 6392 kJ/mol

10 O-H bonds × 463 kJ/mol/bond = 4630 kJ/mol

The total energy released by forming new bonds in the products is:

6392 kJ/mol + 4630 kJ/mol = 11022 kJ/mol

The net change in energy for the combustion of butane is:

11022 kJ/mol - 4436 kJ/mol = 6586 kJ/mol

Finally, we need to calculate the energy change for the given sample of butane (C4H10) by using the Ideal Gas Law:

PV = nRT

where P = 1.3 atm, V = 2.0 L, n is the number of moles of butane, R is the gas constant (0.0821 L·atm/mol·K), and T = 25°C = 298 K.

Solving for n, we get:

n = PV/RT = (1.3 atm)(2.0 L)/(0.0821 L·atm/mol·K)(298 K) = 0.108 mol

Therefore, the change in energy for the given sample of butane (C4H10) is:

6586 kJ/mol × 0.108 mol = 711 kJ

Therefore, the change in energy for the given sample of butane (C4H10) is approximately 711 kJ.

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The electron is moving from energy level 2 to energy level 1 the ground state then the electron emits a photon of EMR. Therefore, option C is correct.

The set distances from an atom's nucleus where electrons may be found are referred to as energy levels. In an atom, the small, negatively charged electrons orbit the central, positively charged nucleus.

The energy of the electron drops when it changes levels, and the atom releases photons. The emission of the photon occurs as the electron transitions from a higher to a lower energy state.

Thus, option C is correct.

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The variables that are not state functions are m (mass), q (heat), and w (work).

Work is an activity that requires physical or mental effort and is done in exchange for money or other rewards. It can also be seen as an exchange of energy, where an individual puts in effort in order to achieve a desired outcome. Work can be done in a variety of fields and can range from manual labor to professional jobs. It is an important part of many people's lives and can be a source of fulfillment and satisfaction, as well as providing a means of economic security. Work can also be a source of stress, but when done properly can be a great way to make a living, develop skills, and better oneself.

Therefore, The variables that are not state functions are m (mass), q (heat), and w (work).

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Carboxylic acids are acidic due to the presence of the carboxyl group. They can react with bases to form salts and water. Alkenes, on the other hand, are not acidic.

Alkenes have a carbon-carbon double bond (-C=C-), while carboxylic acids have a carboxyl group (-COOH). You can identify the functional group by looking at the molecular formula or by using spectroscopic techniques like infrared (IR) spectroscopy.

Carboxylic acids have higher boiling points than alkenes due to the presence of hydrogen bonding between carboxylic acid molecules.

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If the modern penny has a mass of 2.500 g when it is manufactured, but it is mostly zinc metal. The number of  atoms of copper (Cu) that are in a modern penny is: 5.91 x 10^18 atoms of copper (Cu).

To calculate the number of atoms of copper (Cu) in a modern penny, we need to know the atomic mass of copper, which is 63.55 g/mol, and the Avogadro's number, which is 6.022 x 10^23 atoms/mol.

First, we'll calculate the number of moles of copper in the penny by dividing its mass by the atomic mass of copper:

0.0625 g / 63.55 g/mol = 9.84 x 10^-5 mol

Next, we'll multiply the number of moles by Avogadro's number to get the number of atoms:

9.84 x 10^-5 mol * 6.022 x 10^23 atoms/mol = 5.91 x 10^18 atoms

Therefore, there are approximately 5.91 x 10^18 atoms of copper (Cu) in a modern penny.

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Prior to titration, the buret must be cleaned with lab water and the titration solution. With little volumes of lab water, rinse the buret three times.

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The Jobs method works because the ratio of the cations to the anions in a salt is fixed and can be determined by measuring the mass of the precipitate formed when the salt is reacted with a known quantity of a reagent.

What is Job?

In the context of chemistry, the "Jobs method" refers to a chemical technique used to determine the empirical formula of a salt. It is named after its inventor, Zdenko Hans Skraup Job (1865-1933), who was an Austrian chemist and professor of chemistry at the University of Prague.

Job is best known for his work on the synthesis and properties of organic compounds, particularly his research on indole derivatives and alkaloids. He also made important contributions to the field of physical chemistry, including the development of the Jobs method for determining the empirical formula of a salt.

The Jobs method is a chemical technique used to determine the empirical formula of a salt. It involves finding the ratio of the cations and anions in the salt by taking advantage of the precipitation reaction that occurs between the salt and a known amount of a reagent that forms an insoluble product with one of the ions in the salt.

The general steps of the Jobs method are as follows:

A known quantity of the salt is dissolved in water to form a solution.

A known quantity of a reagent is added to the solution, which reacts with one of the ions in the salt to form an insoluble precipitate.

The precipitate is filtered and dried, and the mass is measured.

The mass of the precipitate is used to calculate the moles of the ion that reacted with the reagent.

The ratio of the moles of the cation to the moles of the anion is calculated.

The ratio is then simplified to the smallest whole number ratio to determine the empirical formula of the salt.

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If q > Keq, it means that the reaction quotient, q, has a higher numerical value than the equilibrium constant, Keq and the system is not at equilibrium and will produce more reactants to reach equilibrium (shift to the left).

Therefore, the system is not at equilibrium and will shift in the direction that reduces the value of q and increases the value of Keq, which is toward the side of the reaction with fewer products and more reactants.

In this case, the system will shift to the left (produce more reactants) to reach equilibrium. This suggests that there is an excess of products or a deficiency of reactants in the system compared to what would be present at equilibrium.

Hence the correct option is A.

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Separation into two diametrically opposed social, political, or religious movements.

Polarization, a property of transverse waves, describes the geometric orientation of the oscillations The direction of the oscillation in a transverse wave is the opposite of the wave's motion direction. A simple example of a polarised transverse wave is vibrations along a taut string, as a guitar string. Depending on how the string is pulled, the vibrations can be horizontal, vertical, or at any angle perpendicular to the string. Since the displacement of the oscillating particles always occurs in the direction of the wave's propagation, polarisation does not occur in longitudinal waves, such as sound waves in a liquid or gas.

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The heat that is absorbed is 8.36 kj.

Heat absorbed by ice is the amount of thermal energy that is transferred from its surroundings to the ice, causing the temperature of the ice to increase. This process occurs until the ice reaches its melting point, at which point it begins to convert from a solid state to a liquid state.

We have that;

Q = mcdT

Q = Heat absorbed

m = mass of the substance

c = Heat capacity

dT = temperature change

Thus

Q = 100 * 4.18 * (20)

Q =  8.36 kj

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The given statement: "in general, the bonding within some materials may not be predicted by the Ketelaar triangle. for example, it only accounts for the primary bonding types (metallic, ionic, and covalent)", is true (T) because the Ketelaar triangle indeed only accounts for the primary bonding types and does not consider other bonding types that may exist in some materials.

The Ketelaar triangle is a useful tool for predicting the types of bonding that may occur in a material based on its electronegativity difference. However, it only considers the three primary bonding types: metallic, ionic and covalent. There are other types of bonding, such as hydrogen bonding and van der Waals forces, that may also be present in some materials.

These types of bonding are not accounted for by the Ketelaar triangle, so its predictions may not always be accurate. Therefore while the Ketelaar triangle is a helpful starting point for understanding bonding in materials, it should not be relied upon as the only tool for predicting bonding behavior.

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If 38g of water are produced in the reaction, 19 moles of CO₂ were produced.

The term mole is defined as the amount of substance of a system which contains as many elementary entities.

One mole of any substance is equal to 6.023 × 10²³ units of that substance such as atoms, molecules, or ions. The number 6.023 × 10²³ is called as Avogadro's number or Avogadro's constant.

CO₂ + 4H₂ → CH₄ + 2H₂O

In the above reaction we see that,

2 mole of H₂O produce 1 mol of CO₂

Therefore,

38 gram of  H₂O produce 19gram of CO₂

Thus, If 38g of water are produced in the reaction, 19 moles of CO₂ were produced.

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The enthalpy change of a reaction (ΔHrxn) can be calculated using the heats of formation of each of the reactants and products.

The heat of formation (ΔHf) is the enthalpy change that occurs when one mole of a compound is formed from its constituent elements in their standard states under standard conditions. The standard state is the most stable form of the element at a given temperature and pressure.

The equation for calculating the enthalpy change of a reaction using heats of formation is:

ΔHrxn = Σ(nΔHf(products)) - Σ(nΔHf(reactants))

Where ΔHf is the heat of formation, n is the stoichiometric coefficient, and Σ is the sum of the heats of formation for all species in the reaction.

By using a reference table of heats of formation, we can calculate the enthalpy change for a given reaction and determine if it is exothermic (ΔHrxn < 0) or endothermic (ΔHrxn > 0).

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To calculate the heating value of both solid and liquid fuels, one uses a bomb calorimeter. It is made up of a powerful steel shell called a bomb. It is composed of a base that holds the platinum cross.

What exactly is a solid defined as?

It seems evident what a solid is; a solid is typically thought of as hard and firm. However, closer examination makes the term less clear. For instance, a butter cube is unmistakably a solid since it becomes hard after being kept in a refrigerator. Having stayed on the

A crystalline solid is what?

A solid that has its component atoms and molecules (or occasionally ions) arranged in a crystalline structure microscopic structure is referred to as a crystal lattice (also referred as a crystal). A homogeneous microscopic structure known as a crystal lattice extends across every point of the crystalline solid.

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The molarity of the stoke solution is 14.8 M. Then we need 101.35 ml of the stoke solution with 648.65 ml of distilled water to make 750.0 ml of 2.00 M H₃PO₄ solution.  

Molarity is a common term used to express the concentration of a solution. It is the ratio of number of moles of solute to the volume of solution in liters.

If we have a stoke solution of molarity M1 and volume V1, and the solution prepared from the stoke solution is having molarity M2 and volume V2, then,

M1 V1 = M2 V2.

Given, M1 for the stoke acid solution = 14.8 M

M2 = 2 M

V2 = 750 ml.

then V1 = M2 V2/V1

V1 = 750 ml × 2 M /14.8 M= 101.35 ml.

water to be added to 750 ml = 750 - 101.35 = 648.65 ml

Therefore, you have to combine 101.35 ml of 14.8 M H₃PO₄ with  648.65 ml distilled water to make 750 ml of 2 M solution.

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There are 6.7 * 10^23 oxygen atoms

The mole is a unit of measurement in chemistry used to express amounts of a chemical substance. One mole is defined as the amount of a substance that contains Avogadro's number of entities, which is approximately 6.022 x 10^23 entities

The first step is to get the number of moles of the compound.

Number of moles =85 grams/602 g/mol

= 0.14 moles

Then we have the number of oxygen atoms as;

 0.14 moles * 8 * 6.02 * 10^23

= 6.7 * 10^23 oxygen atoms

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In the figure below, the incomplete resonance structure that is lacking is attached. The addition of the nonbonding electrons and their formal charge, which can be seen from there, completes the resonance structure.

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