electron pairs repel, molecules adjust their shapes so that valence electron pairs are as far apart as possible

A) Valence-shell electron-pair repulsion theory(VSEPR)
B) Electrical Conductivity
C) Lewis Dot Structures
D) Roman numerals

Answer:tells you the identity of the atom

Explanation:

number of protons=atomic number

Answer: C

Explanation: The answer would be C, it tells you the identity of the atom.

Electron configurations for the elements follow 3 principles , Aufbau principle, Pauli Exclusion Principle and Hund's Rule of Multiplicity

What is Aufbau principle ?

It states that electrons fill lower-energy atomic orbitals before filling higher-energy ones.

The order in which the orbitals are filled with electrons are:

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p

Element with electronic configuration of atomic number:

  a.  7 is Nitrogen :  1s2 2s2 2p3 or   [He] 2s2 2p3

  b.  9 is Fluorine :   1s2 2s2 2p5 or [He] 2s2 2p5

  c.  12 is Magnesium : 1s2 2s2 2p6 3s2 or [Ne] 3s2

  d. 36 is Krypton : 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 or [Ar] 4s2 3d10 4p6

Thus we can conclude that electron configurations for the elements follow 3 principles , Aufbau principle, Pauli Exclusion Principle and Hund's Rule of Multiplicity

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If an elephant of mass 500kg stands on the ground, each foot has an area of 0.08m2, the pressure exerted on ground is  15,625 Pa.

In the physical sciences, pressure is defined as the perpendicular force per unit area or the stress at a point within a confined fluid. A 42-pound box with a bottom area of 84 square inches will press down on a surface with a pressure equal to the force divided by the area over which it is applied, or half a pound per square inch.

Atmospheric pressure, which at sea level is roughly 15 pounds per square inch, is the weight of the atmosphere pressing down on each unit area of the Earth's surface. One pascal is equal to one newton per square meter when expressed in SI units, which is how pressure is calculated. Nearly 100,000 pascals of atmospheric pressure are present.

We have given that mass is 500kg and area of each leg is 0.08m²

The formula for Pressure is

Pressure = Force/Area

Let us find the weight first

⇒ weight = mass × g

= 500kg × 10N/kg

= 5000N

Total contact area = 0.08m² × 4

= 0.32m²

Finally, we will calculate the pressure

⇒ Pressure = Force/Area

= 5000N/0.32m²

= 15625 Pa

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The ability of an electric charge or heat to move through a material is measured by its conductivity. A material is considered a conductor if it offers relatively minimal resistance to the flow of thermal or electric energy.

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Answer:

Explanation:

Here, we want to get the mass required to make the given volume

To get this we need to get the number of moles

To get the number of moles, we have to multiply the volume by the molarity

Mathematically, we have that as:

The volume can be converted to liters by dividing by 1000

So we have the volume as 311/1000 = 0.311 L

Thus, we have the number of moles as:

To get the mass, we have to multiply the number of moles by the molar mass

The molar mass of NaCl is 58.44 g/mol

Thus, we have the mass as:

To solve this we need to have knowledge of differential rate law which relate the rate to the concentration and time The option B is correct option.

A differential rate law represents the rate of a reaction . According to this rate is directly proportional to changes in the concentration of reactants and inversely proportional to specific interval of time. There is another expression of rate law which is integrated rate law which is just opposite of differential rate law

The given equation is

[tex]A+3B\rightarrow2C[/tex]

Rate of B= rate of C

[tex]\frac{1}{3}d\frac{[B]}{dt} =\frac{1}{2}d\frac{[C]}{dt}[/tex]

[tex]d\frac{[B]}{dt} =\frac{3}{2}d\frac{[C]}{dt}[/tex]

Thus option B is correct option.

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Answer:

Sulfur has the most neutrons (it has 4).

Among the observations, the mass, which is 3.8 g, describes an extensive property of the material.

Physical properties of a material can be classified as either intensive property or extensive property.

Intensive properties of a material are the properties that do not change no matter how much amount the material changes. On the other hand, extensive properties of a material are the properties that change as the amount of material changes.

Among the given observations, color, texture, and density are all intensive properties. If the unknown sample is increased, these properties will not change.

But when the sample is increased or reduced, the mass will change. Hence, the only extensive property among the observations is the mass.

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The relative contribution of CO2 attributed to global warming is 60 % in the environment.

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ANSWER

Water molecule is a compound

EXPLANATION;

Water molecule is formed from the combination of oxygen and hydrogen atoms

Recall, that compound is the combination of two or more elements that are chemically combined together

Therefore, water molecule is a compound

Equation B. PEa = KEc + PEc best describes the energy at point C, assuming energy is conserved.

As we are provided,

Three particular points A,B and C are described.

The point A is the point at the top, the point B is the point at the bottom and point C is the point somewhere in the middles when merry is swinging.

According to law of conservation of energy,

The sum of total energy is conserved at every point of the motion.

As point A is the highest point. The body will come at momentary rest. The whole of energy will be stored as the potential energy of the girl.

At point B, the swing will have maximum velocity and the whole energy will be found in the form of kinetic energy.

At point C, the total energy will be a sum of potential plus kinetic energy.

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The image shows Mary happily swinging in the park. There are tree positions shown in the image: A, B, and C. PositionB is located at the very bottom of the swing arc and has the lowest height. Which of the following equations best describes the energy at point C, assuming energy is conserved?

A. PEa= KEc

B. PEa= KEc + PEc

C. PEg= KEc + PEc

D. PEg = PEc

Physical change of a substance involves the change in phase or state. The physical change which is endothermic is, conversion of solid carbon to gaseous carbon.

Endothermic reactions are those which absorbs heat energy to give the products. Thus heat is taken into the reaction system hence the name endothermic.

In exothermic reactions, the heat energy is released by the reaction system, where the heat is exiting hence the name exothermic.

When solids changes to gaseous state, the tightly packed molecules in the solid state requires much energy to move apart and to overcome the intermolecular forces of attraction.

Liquid to gas does not require these much energy and gas to liquid evolves energy out.  Therefore, the physical change given here which is  endothermic is conversion of solid carbon dioxide to gas carbon dioxide.

Hence, option D is correct.

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At STP, the volume of oxygen of mass 250g is found to be 175mL.

Volume is the amount of space occupied by an item or substance. Volume is a measurement of how much 3-dimensional space an object occupies. Volume is the measurement of a limited quantity of area at a specific end.

Mass is a measurement of the quantity of matter in an item or substance. Mass is the physical quantity that represents the amount of matter in an object's body. The amount of weight accommodated in an item or stuff is measured in mass.

Density - The amount of space taken up by an item or substance (its volume) in proportion to the amount of matter in that thing or substance (its mass).

Given:

Mass = 250g = 0.25kg

Density at STP = 1.4291g/L

To find:

Volume = ?

Formula:

Density = Mass / Volume

Calculations:

Volume = Mass / Density

Volume = 0.25 / 1.4291

Volume = 0.175L

Volume = 175mL

Result:

The volume of oxygen of mass 250g is found to be 175mL at STP.

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The ph after 25.0 ml of the naoh solution have been added is 1.222.

You are aware that the balanced chemical equation states that sodium hydroxide and hydrochloric acid balance each other out in a 1:1 mole ratio.

NaOH (l) + HCl (l) = NaCl (l) + H2O (l)

As a result, equal amounts of sodium hydroxide and hydrochloric acid must be used to completely neutralize a substance, producing a neutral solution with a pH of 7 at ambient temperature.

Although the molarities of your two solutions are equivalent, the hydrochloric acid solution has a volume of 100 mL divided by 25.0 mL, which equals four.

[tex][H3O+]=(75⋅0.100103).moles H3O+125⋅103.L=(75⋅0.100125)mol L−1This means that you havepH=−log(75⋅0.100125)=1.222−−−−−[/tex]

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Answer: the answer is D) The first equation should be multiplied by 9 and the second equation by −4.

Explanation:edge 2022

Answer:

Barium sulfate, BaSO4, is made by reacting barium hydroxide and other barium sources with sulfuric acid and has a long history as a translucent white pigment.

The correct answer is option C: Catalyst

A substance that helps a reaction to take place, but does not participate in the reaction is called a catalyst.

In Chemistry, a catalyst is defined as a substance that increases the rate of a chemical reaction without itself undergoing any changes. This process is called catalysis.

There are 3 different types of catalysts: enzymatic, homogeneous, and heterogeneous.

The catalytic substance remains unchanged and does not consume during the reaction, Their only job is to speed up the reaction by breaking bonds and saving time and energy.

For example, during the commercial preparation of ammonia also called the 'Haber process' iron is added as a catalyst to accelerate the reaction rate.

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Moving across the period the elements gain a proton and gain a valence electron.

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The element that have been described in the question above is Strontium.

The term first ionization energy refers to the energy that is required in order to remove the first electron from the valance shell of an atom. We know that the first ionization energy of an atom depends on some factors such as the proximity of the outermost shell to the nucleus of atom.

As such, the element that is being discussed here is the strontium atom. It has  a lower first ionization energy than calcium and  a smaller atomic radius than barium.

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The average molar mass of sulfur is 32.84g/mol

The average atomic mass of a chemical element is calculated by taking into account the atomic masses of its naturally occurring isotopes and their respective abundances

Here given data is natural sulfur consists of three isotopes :

95.0% sulfur-32 = 31.97 amu

0.75% sulfur-33 = 32.97 amu

4.21% sulfur-34 = 33.96 amu

So, we have to find average molar mass of the sulfur = ?

Formula for average molar mass = ∑i × isotope i  × abundance i

³²S = 95.0% abundance = 31.97 amu

³³S = 0.75% abundance = 32.97 amu

³⁴S = 4.21% abundance = 33.96 amu

This means that average molar mass of sulfur is

Average molar mass = 31.97 amu×95.0 +  32.97 amu× 0.75 + 33.96 amu×4.21

Average molar mass = 32.84g/mol

Average molar mass of sulfur is 32.84g/mol

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1.enthalpy ΔH = -45.1872 Kj/mol

2.enthalpy ΔH = -2.092 Kj/mol

3.enthalpy ΔH = -13.888 Kj/mol

A thermodynamic system's internal energy and the product of its pressure and volume are added to form enthalpy, which is one of the system's properties. It is a state function that is frequently used to monitor chemical, biological, and physical systems at a constant pressure that is conveniently given by the sizable surrounding environment. The labor necessary to determine the system's physical dimensions, or to make room for it by displacing its surrounds, is expressed by the pressure-volume phrase. Under typical conditions, the pressure-volume term is very small for solids and liquids and moderately small for gases. As a result, in chemical systems, enthalpy serves as a stand-in for energy; bond, lattice, solvation, and other concepts referred to as "energies" in chemistry are actually differences in enthalpy.

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The intermolecular forces in HF, [tex]CCl_4[/tex] and [tex]CH_3Cl[/tex] molecules are hydrogen bonding, dispersion forces and dipole-dipole interactions respectively.

Intermolecular forces, such as the electromagnetic forces of attraction or repulsion that act between atoms in a molecule and other kinds of nearby particles, such as atoms or ions, mediate interactions between molecules.

The attractive forces that occur between molecules are known as intermolecular forces. They control a number of bulk characteristics, including the solubilities (miscibilities) of compounds and their melting and boiling temperatures.

Intermolecular forces may be divided into four categories: hydrogen bonding, London dispersion forces, ion-dipole, and dipole-dipole.

HF has a hydrogen bond, also known as an H-bond, is an electrically charged attraction between an electronegative atom containing a single pair of electrons, known as the hydrogen bond acceptor, and a hydrogen (H) atom that is covalently attached to a more electronegative "donor" atom or group.

[tex]CCl_4[/tex] has London dispersion forces which is the least powerful intermolecular force. When the electrons in two nearby atoms hold positions that cause the atoms to temporarily form dipoles, the consequence is the London dispersion force, a transient attractive attraction.

[tex]CH_3Cl[/tex] has dipole-dipole interactions where molecules having permanent dipoles are drawn to one another electrostatically; for example, the positive end of one molecule will attract the negative end of another, and so forth, eventually causing the molecules to align.

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In case of exothermic or endothermic reactions  where heat is  absorbed  or released  there is a need to measure specific heat, change in temperature and time to heat.

An exothermic reaction is defined as a chemical reaction which involves release of energy in the form of light,heat .In these reactions, energy is transferred from system to surroundings rather than taking energy from surroundings into system as in endothermic reactions.

In an exothermic reaction,change in enthalpy is negative.Therefore, it can be inferred that net amount of energy which is required to start the exothermic reaction is less than the net amount which is released by the reaction.

Examples of exothermic reactions are combustion reactions, detonation of nitroglycerin , neutralization reactions and nuclear fission.

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Each solution has a concentration of 7.625 x 103 m, 3.8125 x 104 m, and 1.90625 x 105 m, respectively.

Dilution is the process of lowering a sample's concentration by incorporating more solvent, according to its definition. The following is the dilution formula.

C₁V₁ = C₂V₂

where C1 is the sample's initial concentration.

V1 is the initial sample volume.

After dilution, the ultimate concentration is C2.

After dilution, the ultimate total volume is V2.

Calculate the concentration of the diluted solution by entering the numbers into the formula.

first common answer

C₁V₁ = C₂V₂

0. 1525 m(5.00 ml) = C₂(100.0 ml) (100.0 ml)

C₂ = 7.625 x 10⁻³ m

Second common solution

C₁V₁ = C₂V₂

7.625 x 10⁻³ m(5.00 ml) = C₂ (100.0 ml)

C₂ = 3.8125 x 10⁻⁴ m

Third accepted option

C₁V₁ = C₂V₂

3.8125 x 10⁻⁴ m(5.00 ml) = C₂(100.0 ml) (100.0 ml)

C₂ = 1.90625 x 10⁻⁵ m

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After one half life, the number of years needed for 1/4 of the cobalt-60 to remain after decay is computed as follows.

After another half life, only 1/4 of the original mass isotope is left; consequently, if one half life is 5.3 years, the number of years needed is 2 x 5.3 years, or 10.6 years.

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The amount of CO₂ formed is 44g.

The chemical reaction occurs is C+O₂=CO₂.

We know that 1mol of carbon and 2 oxygen reacts together to form 1mol of CO₂.

According to law of conservation of mass the total mass of the products formed in chemical reaction must be equal to the mass of reactants consumed.

So, the amount of CO₂ produced is 1mol of CO₂ is 44g, which is equal to it’s molecular weight.

According to the law of conservation of mass, mass is neither generated nor destroyed during a chemical process. For instance, when coal is burned, the carbon atom in it transforms into carbon dioxide. The carbon atom transforms from a solid to a gas, yet its mass remains constant.

CO₂ gas has no color or smell. The gas is not combustible. It has a mild toxicity. Denser than air, it. It is soluble in water, and as temperature rises, solubility decreases.

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Answer

0.113 M

Explanation

Given that:

The volume of the stock solution, V₁ = 50.0 mL

The concentration of the stock solution, C₁ = 1.74 M

The volume of the solution the chemist made, V₂ = 770.0 mL

What to find:

The concentration (C₂) of the BaCl₂ solution the chemist made.

Step-by-step solution:

The concentration (C₂) of the chemist's working solution can be calculated using the dilution formula below:

Hence, the concentration of the chemist's working solution is 0.113 M.