A theory that has been proven true repeatedly over time and never disproven is called ??

Answer: Option (c) is the correct answer.

Explanation:

Neon has atomic number 10 and its electronic distribution is 2, 8. As it has completely filled valence shell therefore, it does not need to gain or lose an electron.

Hence, neon is stable in nature and does not form bonds with any other atom.

Whereas atomic number of gold is 79 and its electronic configuration is [tex][Xe] 4f^{14}5d^{10}6s^{1}[/tex]. Hence, in order to attain stability, it loses one electron and thus, it is likely to form a bond.

Oxygen atom has atomic number 16 and its electronic distribution is 2, 8, 6. Hence, to attain stability it needs 2 electrons. Hence, it is likely to form a bond.

Magnesium has 2 valence electrons and chlorine has 7 valence electrons. So, they combine chemically to form [tex]MgCl_{2}[/tex].

Thus, we can conclude that out of the given options neon atoms are not likely to form bonds.

Amanda dropped a rock into a graduated cylinder containing water. The water level in the cylinder increased. Density is the  property of the rock.

Density is the mass of a specific material per unit volume. d = M/V, at which d is density, M is weight, and V is volume, is the formula for density. Grams per cubic centimeter are a typical unit of measurement for density. For instance, whereas Earth has a density of 5.51 grams, water has a density of 1 grams.

Another way to state density is in kilograms per cubic meter (in metre-kilogram-second or SI units). For instance, air weighs 1.2 pounds per cubic metre. Amanda dropped a rock into a graduated cylinder containing water. The water level in the cylinder increased. Density is the  property of the rock.

Therefore, the correct option is option A.

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This organism would be found in a marine ecosystem.

The pressure of the hydrogen gas collected by water displacement at a temperature of 26°C is obtained by measuring the height of the displaced mercury, considering the presence of water vapor and it is calculated as 725 torr.

The question is requesting the pressure of hydrogen gas collected by water displacement at a temperature of 26°C. The pressure of a gas sample can be determined using a variety of methods. One such approach is measuring the displacement of a column of mercury. If the column of mercury is 26.4 cm high, the pressure of the gas is equivalent to this height, or 264 torr.

However, the presence of water vapor can affect the calculated pressure of the gas. At 26°C, the pressure of water vapor is 25.2 torr. Hence, we need to subtract this value from the total pressure to obtain the pressure of hydrogen gas.

Therefore, the pressure of the hydrogen gas collected by water displacement at a temperature of 26°C is 725 torr.

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The pressure of the collected hydrogen gas is equal to the atmospheric pressure.

A sample of hydrogen gas was collected by water displacement at 26°C. To determine the pressure of the collected hydrogen gas, we need to consider the relationship between pressure, volume, temperature, and the number of moles of gas.

Using the ideal gas law, we can calculate the number of moles of hydrogen gas from the volume and temperature. Then, using the molar mass of hydrogen gas, we can determine the mass of the collected gas. Finally, we can relate the mass of the gas to the pressure using the density formula.

Since the hydrogen gas was collected by water displacement, we can assume that it occupies the same volume as the displaced water. Given the temperature of 26°C (299 K) and assuming atmospheric pressure (1 atm), we can calculate the number of moles of hydrogen gas using the ideal gas law.

Once the number of moles is known, we can determine the mass of the hydrogen gas using its molar mass (2.016 g/mol). Finally, we can calculate the pressure of the gas using the density formula, considering the mass of the gas and the volume of the displaced water.

Therefore, the pressure of the collected hydrogen gas is approximately 1 atm, which is the same as the atmospheric pressure.

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Taking into account the definition of density and Avogadro's number,  1.44×10²⁴ molecules of ethanol are present in 140 ml of ethanol.

Density is defined as the property that matter, whether solid, liquid or gas, has to compress into a given space.

In other words, density is a quantity that allows us to measure the amount of mass in a certain volume of a substance. Then, the expression for the calculation of density is the quotient between the mass of a body and the volume it occupies:

[tex]density=\frac{mass}{volume}[/tex]

Avogadro's Number

Avogadro's Number or Avogadro's Constant is called the number of particles that make up a substance (usually atoms or molecules) and that can be found in the amount of one mole of said substance. Its value is 6.023×10²³ particles per mole. Avogadro's number applies to any substance.

In this case, you know that:

Replacing in the definition of density:

[tex]0.789\frac{g}{cm^{3} } =\frac{mass}{140cm^{3} }[/tex]

Solving:

mass= 0.789 [tex]\frac{g}{cm^{3} }[/tex]×140 cm³

mass= 110.46 g

The molar mass of ethanol, that is, the amount of mass present in one mole of the compound, is 46 [tex]\frac{g}{mol}[/tex]. Then the number of moles that 110.46 g of ethanol contain is calculated by:

110.46 g×[tex]\frac{1 mol}{46 g}[/tex]= 2.40 moles

Finally, you can apply the following rule of three: If by definition of Avogadro's number 1 mole of ethanol contains 6.023×10²³ molecules, 2.40 moles contains how many molecules?

amount of molecules= (2.40 moles× 6.023×10²³ molecules)÷ 1 mole

amount of molecules= 1.44×10²⁴ moles

In summary, 1.44×10²⁴ molecules of ethanol are present in 140 ml of ethanol.

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To find out how many molecules of ethanol are in 140 mL of ethanol with a density of 0.789 g/cm³, convert the volume to mass using the density, the mass to moles using the molar mass and moles to molecules using Avogadro's number, yielding approximately 1.44 × 10²´ molecules.

To calculate how many molecules of ethanol are present in 140 mL of ethanol, with a density of 0.789 g/cm³, we'll follow these steps:

We can start by finding the mass:

Then, we convert mass to moles:

And then convert moles to molecules:

So, there are approximately 1.44 × 10²´ molecules of ethanol in 140 mL of ethanol.

To solve this, we must first find the value of the wavelength using the formula:

1/ʎ = R [1/(nfinal)^2 – 1/(ninitial)^2]

where ʎ is wavelength and R is Rydberg’s constant = 10,973,731.6 m-1

1/ʎ = 10,973,731.6 m-1 [1/2^2 – 1/4^2]

1/ʎ = 2,057,574.675 m-1

ʎ = 4.86 x 10^-7 m

Then compute for energy using the equation:

E = hc / ʎ

where h is Plancks constant = 6.63 x 10^-34 J s, c is speed of light = 3 x 10^8 m/s

E = (6.63 x 10^-34 J s) (3 x 10^8 m/s) / 4.86 x 10^-7 m

E = 4.09 x 10^-19 J

Electrons are the smallest of the three particles that make up atoms. Electrons are found in shells or orbitals that surround the nucleus of an atom. Protons and neutrons are found in the nucleus. They group together in the center of the atom.

The electron shell of an atom contains electrons, negatively charged subatomic particles. Protons and neutrons, the other subatomic particles, reside in the atom's nucleus.

The electron shell of an atom contains one type of subatomic particle known as the electron. Electrons are very small particles with a negative charge, often represented by 'e⁻' in scientific notation. In contrast, two other subatomic particles, the proton and neutron, are located in the nucleus of the atom. Protons have a positive charge and are denoted by 'p⁺', while neutrons have no charge and are represented by 'n' or 'n⁰'. The combination of electrons, protons, and neutrons constitutes the fundamental architectural makeup of an atom, determining its element, isotopes, and chemical behavior.

> How many valence electrons does a helium atom have?

The electron configuration of Helium is simply 1s2. We see that its outermost shell is the s shell and it contains 2 electrons, therefore the number of valence electrons is also 2.

> What is the formula of the ion formed when potassium achieves noble-gas electron configuration?

Potassium has a electron configuration of [Ar] 4s1. To have an electron configuration of only [Ar] which is a noble gas, the one electron from 4s1 should be removed, hence:

K+

Sodium chloride is soluble in water but silica does not. Hence, addition of water to the sample will separate sodium chloride out.

There are various methods to separate the individual chemical compounds from a mixture of them based on their physical or chemical properties. Distillation, filtration, chromatography, magnetic separation etc are some of the separation methods.

Based on the solubility of compounds, the salts can be separated using a separating funnel by adding a suitable solvent.

For example an acid and its salt can be separated by adding an inorganic acid solvent where the salt is soluble and forms aqueous layer and the acid forms a separate organic layer.

Sodium chloride is highly soluble in water, whereas, silica does not dissolve in water. Because of the presence of oxide layer on silica it is insoluble in water.

Thus, by adding water to the sample the silica will deposits under and the salt solution can be removed out.

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Answer:

Option B.Mitochondria

Explanation:

I took a unit test and this question was on it, the mitochondria is the correct answer

Hope this helps

Final answer:

Carbon dioxide is produced as a byproduct of cellular respiration, where sugar reacts with oxygen to release energy, water, and CO2. The CO2 is then transported to the lungs as bicarbonate and exhaled.

Explanation:

We inhale oxygen (O2) and exhale carbon dioxide (CO2). Carbon dioxide is produced in the body because every cell requires oxygen for the oxidative stages of cellular respiration, a process by which energy is produced in the form of adenosine triphosphate (ATP). During this process, sugar (C6H12O6) reacts with oxygen to produce carbon dioxide, water, and energy according to the balanced equation: C6H12O6 + 6O2 → 6CO2 + 6H2O + energy.

Carbon dioxide is then transported back to the lungs as bicarbonate via the bloodstream, where it dissociates readily from hemoglobin and diffuses across the respiratory membrane into the air within the alveoli to be expelled as a waste product.

Final answer:

Carbon dioxide is produced as a byproduct of cellular respiration, during which cells use oxygen to convert nutrients into energy, and is excreted by exhaling after being carried to the lungs in the form of bicarbonate.

Explanation:

We inhale oxygen when we breathe, which is essential for the process of cellular respiration. In this process, our cells use oxygen to convert nutrients, such as sugars, into energy in the form of adenosine triphosphate (ATP), carbon dioxide , and water. Carbon dioxide is produced as a waste product during the oxidative stages of cellular respiration. It is then transported back to the lungs via the blood, where it is converted largely into bicarbonate ions by the enzyme carbonic anhydrase within red blood cells.

The high concentrations of carbon dioxide in areas of high metabolic rate lead to its diffusion into blood capillaries and eventual transport to the lungs. Gas exchange within the alveoli of the lungs allows carbon dioxide to be exhaled and fresh oxygen to be taken up by the bloodstream, continuing the cycle of respiration. The respiratory quotient (RQ) can vary depending on the type of nutrient being metabolized—fats, proteins, or carbohydrates—but it generally represents the ratio of carbon dioxide produced to oxygen consumed.

Assessing the maximum number of cross-linkages from vulcanizing 100 g of polyisoprene is not possible without detailed conditions of vulcanization. Vulcanization creates cross-linkages at different densities for various rubber characteristics, with 2-3% and 25-35% crosslinking producing soft and hard rubber, respectively.

The question "What is the greatest number of theoretical cross-linkages possible by vulcanizing 100 g of polyisoprene chains?" pertains to the chemical process of vulcanization, which is used to strengthen rubber. Vulcanization involves adding sulfur or other curatives to polymers, like polyisoprene, which creates cross-linkages between the polymer chains. This process transforms rubber into a more durable, elastic material commonly used in a variety of products including tires and seals.

However, without specific information on the conditions of vulcanization, such as the amount of sulfur or the extent of heat applied, or the exact structure of the polyisoprene used, it is impossible to calculate the exact maximum number of cross-linkages. What we can acknowledge is that cross-linkages occur at varying densities depending on the desired characteristics of the rubber produced. For example, at 2 to 3% crosslinking, a soft rubber suitable for many everyday applications is obtained, while at 25 to 35% crosslinking, a hard rubber product is achieved.

the greatest number of theoretical cross-linkages possible by vulcanizing 100 g of polyisoprene chains is approximately[tex]\(1.77 \times 10^{24}\).[/tex]

The number of theoretical cross-linkages possible by vulcanizing polyisoprene chains depends on the number of repeat units in the polymer and the stoichiometry of the vulcanization reaction. Vulcanization typically involves the formation of sulfur bridges between polymer chains, leading to cross-linkages.

Polyisoprene (natural rubber) is a polymer composed of repeating isoprene units [tex](\(C_5H_8\)).[/tex] The molar mass of isoprene is approximately 68.12 g/mol.

To find the number of moles of polyisoprene in 100 g, we divide the mass by the molar mass:

[tex]\[ \text{Moles of polyisoprene} = \frac{\text{Mass of polyisoprene}}{\text{Molar mass of polyisoprene}} \][/tex]

[tex]\[ \text{Moles of polyisoprene} = \frac{100 \, \text{g}}{68.12 \, \text{g/mol}} \][/tex]

[tex]\[ \text{Moles of polyisoprene} \approx 1.47 \, \text{mol} \][/tex]

Now, let's assume that each cross-linkage involves one sulfur atom (S). The molar mass of sulfur is approximately 32.07 g/mol.

For every mole of polyisoprene, a certain ratio of sulfur atoms is used in the vulcanization process. This ratio depends on the specific vulcanization method and conditions. Let's assume a simplified scenario where each isoprene unit can potentially form a cross-linkage with a sulfur atom.

The molar ratio of sulfur atoms to isoprene units is 1:1. Therefore, the number of moles of sulfur required is the same as the number of moles of polyisoprene.

[tex]\[ \text{Moles of sulfur} = 1.47 \, \text{mol} \][/tex]

Now, let's calculate the number of sulfur atoms:

[tex]\[ \text{Number of sulfur atoms} = \text{Moles of sulfur} \times \text{Avogadro's number} \][/tex]

[tex]\[ \text{Number of sulfur atoms} = 1.47 \times 6.022 \times 10^{23} \][/tex]

[tex]\[ \text{Number of sulfur atoms} \approx 8.84 \times 10^{23} \][/tex]

Each sulfur atom can potentially form two cross-linkages (one with each isoprene unit). Therefore, the maximum number of theoretical cross-linkages possible is twice the number of sulfur atoms.

[tex]\[ \text{Maximum number of theoretical cross-linkages} = 2 \times \text{Number of sulfur atoms} \][/tex]

[tex]\[ \text{Maximum number of theoretical cross-linkages} = 2 \times 8.84 \times 10^{23} \][/tex]

[tex]\[ \text{Maximum number of theoretical cross-linkages} \approx 1.77 \times 10^{24} \][/tex]

So, the greatest number of theoretical cross-linkages possible by vulcanizing 100 g of polyisoprene chains is approximately[tex]\(1.77 \times 10^{24}\).[/tex]

156251.099 grams of O₂ are required to burn 17.0 gal of C₈H₁₈

Density is a quantity derived from the mass and volume

Density is the ratio of mass per unit volume

With the same mass, the volume of objects that have a high density will be smaller than objects with a smaller type of mass

The unit of density can be expressed in g / cm³ or kg / m³

Density formula:

[tex]\large{\boxed{\bold{\rho~=~\frac{m}{V} }}}[/tex]

ρ = density

m = mass

v = volume

1 gal equal to = 3785.41 ml

then 17.0 gal = 17 x 3785.41 = 64351.97 ml Octane

grams Octane = ρ x ml

grams Octane = 0.692 g.ml x 64351.97

grams Octane = 44531.563

molar mass Octane (C₈H₁₈) = 114

mole Octane = grams : molar mass

mole Octane = 44531.563  : 114

mole Octane = 390.627

From the reaction

C₈H₁₈ + 25/2 O₂ ⇒ 8 CO₂ + 9H₂O

mole C₈H₁₈ : mole O₂ = 1 : 25/2

[tex]mole\:O_2\:=\:\frac{25}{2} \times\:390.627[/tex]

mole O₂ = 4882.846

grams O₂ = mole x molar mass

grams O₂ = 4882.846 x 32

grams O₂ = 156251.099

moles of water

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Keywords: Octane,  mole, mass, gal, density

"[tex]1.56\times 10^5 \ g[/tex]" of [tex]O_2[/tex] are required to burn 17.0 gal of [tex]C_8 H_{18}[/tex].

According to the question,

We know that,

then,

Now,

→ Mass of Octane will be:

= [tex]0.692\times 64352[/tex]

= [tex]44531 \ g[/tex]

or,

→ [tex]114 \ g \rightarrow 400 \ g[/tex]

→ [tex]44531 \ g \rightarrow \frac{400\times 44531}{114}= 156251 \ g[/tex]

hence,

The Oxygen (O₂) needed will be:

= [tex]1.56\times 10^5 \ g[/tex]            

Thus the above answer is appropriate.

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answer: 43 grams.

This problem is a good example to understand  the law of conservation of mass. This law states that mass can neither be created nor destroyed , meaning that the final mass is the same that what you started with..

You didn't measure the weight of the oxygen that entered the reaction, so the weight of the rustic nail, plus the weight of the oxygen, will be the equal to the final mass. 

100 +43 = 143g 

Answer:

43 Grams:) I hope that this helped!

Final answer:

An element that has 54 electrons and a +2 charge is iron, resulting in an Fe2+ ion, also known as the iron(II) ion. For the given exercise, an ion with 34 protons and 36 electrons is a Se2- ion, known as the selenide ion.

Explanation:

The element that forms an ion with 54 electrons and a charge of +2 can be identified by first finding the number of protons in its neutral state, which remains unchanged when it becomes an ion.

Since the element has a +2 charge, it must have two more protons than electrons, giving it a total of 56 protons, which is the atomic number of iron (Fe). Therefore, the element is iron, and the ion is Fe2+, also known as the iron(II) ion or ferrous ion.

Now, to answer the check your learning question: An ion with 34 protons and 36 electrons has two more electrons than protons, indicating a -2 charge. The element with 34 protons is selenium (Se), and the ion is Se2-, known as the selenide ion.

The activity that most resembles atoms in a liquid state would be the soccer players running randomly in all directions, as this mirrors the constrained yet random motion atoms in a liquid state experience.

The student was likely comparing soccer players to atoms in a liquid state in order to describe the random, yet constrained movement atoms in a liquid experience. This is best mirrored by the soccer players if they are 'Running randomly in all directions' (Option C). In a liquid state, atoms are not rigidly fixed in place but nor do they have the freedom to move indefinitely in any direction, unlike in a gaseous state.

The other options, such as players lining up or huddling around the ball, would suggest more organized or confined states- more reminiscent of the solid state. Jumping up and down, depending on the speed and proximity to each other, could either be reminiscent of atoms in a solid state (slow movement, confined within certain boundaries) or a heated liquid/gas state (faster movement, possibility to overcome interatomic forces).

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Answer:

some mass of the nucleus was lost in the first nuclear reaction.

Explanation:

In a nuclear reaction, mass is converted to energy according to Einstein's equation;

E=∆mc^2 where ∆m is known as mass defect. The mass defect arises due to the conversion of part of the mass of the nucleus into energy in a nuclear reaction. c is the speed of light 3×10^8 ms^-1

By so doing, Albert Einstein confirmed that mass and energy are inter convertible in a nuclear reaction.

Final answer:

Evaporation of water is a physical change because it involves a change from liquid to gas without altering the chemical composition of the water (H₂O). The water molecules remain the same before and after evaporation.

Explanation:

The evaporation of water is a physical change, not a chemical one. During the evaporation process, liquid water (H₂O (l)) turns into water vapor (H₂O (g)), but the molecular structure of water does not change. The molecules gain energy and move apart to transition from the liquid to the gas phase, but they remain as H₂O molecules throughout this process, indicating that no chemical reaction has occurred, only a change in state.

Examples of physical changes include the dissolving of sugar in water, the melting of solid gold, and the conduction of energy through a material. None of these processes result in a change to the underlying chemical composition of the substance involved. For example, even when sugar dissolves in water, it still remains sugar and can be recovered by evaporating the water.