How many kilograms are there in 81. 2 Mg? Express your answer in scientific notation

The correct option is C .The difference between first- and second-order reactions is that the rate of a first-order reaction depends on reactant concentrations, whereas the rate of a second-order reaction does not depend on reactant concentrations.

The order of a reaction is determined by the power to which the concentration of each reactant is raised in the rate law. A first-order reaction is a chemical reaction in which the rate of reaction is proportional to the concentration of only one reactant (unimolecular reaction), and the rate equation can be expressed in terms of the concentration of the reactant as d[A] /dt = - k[A], where [A] is the concentration of the reactant and k is the rate constant. Second-order reactions are chemical reactions in which the rate of reaction is proportional to the square of the concentration of one reactant, or proportional to the product of the concentrations of two reactants (bimolecular reaction).

However, The rate of a first-order reaction does not depend on the initial concentration of the reactant, whereas the half-life of a first-order reaction depends on the initial concentration. On the other hand, the rate of a second-order reaction does depend on reactant concentrations, whereas the half-life of a second-order reaction does not depend on the initial concentration.

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After the CO₂ was released from the lake, the normal air was displaced by the heavier CO₂. This option is correct.

CO₂, or carbon dioxide, is a gas that is slightly heavier than air. The density of CO₂  is approximately 1.98 kg/m³, whereas the density of air is around 1.2 kg/m³.

This means that CO₂  is denser than air and has a greater mass per unit volume. When CO₂ is released from a lake, it will displace the normal air in the surrounding area because of its higher density.

The normal air stayed where it was originally, and it did not displace the heavier CO₂  since CO₂ is heavier than air.

So, the correct option is "the normal air was displaced by the heavier CO₂ ."

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Answer:

jkhihjijhbjbjk

If a neutral object lost two electrons, it would have a positive charge.

Electrons are negatively charged subatomic particles that orbit around the positively charged nucleus in an atom. When an atom loses electrons, it becomes positively charged because the total negative charge from the electrons is reduced. The number of electrons in an atom determines its overall charge, and when electrons are lost, the atom's charge becomes more positive.

In this case, the neutral object would have a net positive charge equal to the number of protons in its nucleus, since it has lost two negatively charged electrons. Thus, the object would be positively charged after losing two electrons.

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The rate constant k for the reaction is 3.84 x 10⁻³ s⁻¹.

The second-order rate law is expressed as:

rate = k [A]²

where;

The integrated rate law for a second-order reaction is:

1/[A]t - 1/[A]0 = kt

where;

Substituting the given values into the equation, we get:

1/1.38 - 1/2.91 = k(189)

0.7246 = k(189)

k = 0.7246/189

k = 3.84 x 10⁻³ s⁻¹ (to three significant figures in scientific notation)

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Answer:

Step 1: Determine the molecular weight of water. The molecular weight of water is 18.015 g/mol.

Step 2: Calculate the number of moles. To calculate the number of moles, divide 90g by the molecular weight of water to get 5 moles of water.

Step 3: Calculate the number of atoms of water present. One mole of water contains 6.022 x 10^23 molecules of water. Therefore, 5 moles of water contains (5 x 6.022 x 10^23) = 3.011 x 10^24 atoms of water.

Therefore, there are 3.011 x 10^24 atoms of water present in 90g of water.

The correct answer is D.

A strong base is a substance that completely dissociates into its ions in water, producing a high concentration of hydroxide ions (OH-). Similarly, a weak base is a substance that only partially dissociates into its ions in water, producing a low concentration of hydroxide ions (OH-).

The term that completes the analogy is "Weak electrolyte", which is a substance that only partially dissociates into its ions in water and conducts electricity poorly. A strong electrolyte, on the other hand, is a substance that completely dissociates into its ions in water and conducts electricity well.

Therefore, the analogy can be completed as follows:

"Strong base is to weak base as strong electrolyte is to weak electrolyte."

I hope it helped you :)

The new volume of the helium gas sample will be  124 ml. This is due to the fact that when the temperature decreases while the pressure remains constant, the volume of a gas will increase.

According to Charles’s law, the volume of a given gas at a constant pressure is directly proportional to its absolute temperature. Therefore, a decrease in temperature, while holding constant the pressure of the helium gas, would result in a decrease in volume.

A constant pressure is the one under which the pressure of a substance remains unchanged as the temperature and/or volume of the substance change. Charles's law may be used to explain the properties of gases, particularly with constant pressure since it states that the volume of a given mass of a gas is directly proportional to its absolute temperature, provided that its pressure remains constant. It's written as:V1/T1 = V2/T2; whereV1 = 620 ml; T1 = 500K; T2 = 100KLet's put the values in the formula given above. The [tex][tex]620/T1 = V2/100V2 = 62,000/500V2 = 124 ml[/tex].[/tex]Therefore, the new volume of helium gas at a temperature of 100K would be 124 ml.

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Yes, a precipitate will form if you mix together 100 mL of 0.010 m calcium chloride with 100 mL of 1.0 x 10-5 m solution of potassium carbonate.

This is because the Ksp (solubility product constant) for calcium carbonate is 3.0 x 10-9. This means that when the concentrations of calcium and carbonate ions become too high, they will no longer be soluble and a precipitate will form. To understand this better, consider the following reaction:

CaCl2 (aq) + CO3 (aq) --> CaCO3 (s) + 2Cl- (aq).

This equation shows that calcium ions (Ca2+) from the calcium chloride solution will react with carbonate ions (CO3-) from the potassium carbonate solution to form solid calcium carbonate (CaCO3) and chloride ions (Cl-). When the concentrations of calcium and carbonate ions in the solution become too high, a precipitate will form as calcium carbonate.

The Ksp for calcium carbonate is a measure of how much calcium and carbonate ions can be present in the solution before a precipitate forms. This means that if the concentrations of the calcium and carbonate ions become greater than 3.0 x 10-9 molar, a precipitate will form. The concentrations of the calcium and carbonate ions in the given solutions are 0.010 m and 1.0 x 10-5 m respectively, both of which are greater than the Ksp of calcium carbonate and hence a precipitate will form.

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Answer: d. possessing tiny protrusions known as microvilli. The proximal convoluted tubule's epithelial cells have microvilli on their surface, which increases their surface area and improves.

the efficiency of reabsorption of chemicals from the filtrate back into the circulation. The cells do not release enzymes to promote absorption, and the rugae folds and thin walls are not adaptations for reabsorption. The proximal convoluted tubule's epithelial cells are in charge of reabsorbing vital components from the glomerular filtrate, including glucose, amino acids, and electrolytes. Many microvilli, which are tiny finger-like projections on the surface of the cell that enhance the surface area accessible for reabsorption, are present in the cells, which enable them to perform this role. This modification makes it possible for chemicals to be reabsorbted more effectively as they move through the tubule. The rugae folds and thin walls, on the other hand, have little impact on reabsorption in the proximal convoluted tubule. In this region of the nephron, reabsorption likewise does not include enzyme secretion.

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The switch from ¹⁵NH₄Cl to ¹⁴NH₄Cl for three generations (an eightfold increase in population) in a culture of E. coli will result in a molar ratio of hybrid DNA ( ¹⁵N-¹⁴N) to light DNA (¹⁴N-¹⁴N) of 3:1.

The reason for this is that during the first replication cycle in the ¹⁴NH₄Cl-containing medium, the hybrid DNA strands will split, and half of the daughter DNA molecules will contain a heavy ¹⁵N nitrogen atom and a light ¹⁴N nitrogen atom.
The remaining daughter DNA molecules will have two light ¹⁴N nitrogen atoms, resulting in a molar ratio of 1:1.

During the next replication cycle, the hybrid DNA strands, in the light ¹⁴NH₄Cl-containing medium, will split once again, and the resulting daughter DNA molecules will either have one heavy and one light nitrogen atom or two light nitrogen atoms. Thus there will be 2 hybrid DNA and 2 pure DNA with light nitrogen, resulting in the same molar ratio of 1:1.

In the next cycle, the 2 molecules with light nitrogen give 4 pure molecules and 2 more pure molecules come from the strand of each hybrid molecule. Thus there is a total of 6 pure molecules. The heavy nitrogen strand of the hybrids gives rise to 2 more hybrids. So, there is a total of 2 hybrids and 6 light nitrogen molecules, resulting in a molar ratio of 3:2.

Therefore, the molar ratio of hybrid DNA ( ¹⁵N-¹⁴N) to light DNA (¹⁴N-¹⁴N) of 3:1.

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The volume of Neon gas is 326.5 L in 8. 9 * 10 ^ 25 atoms as per the ideal gas law equation.

The given atoms of Neon gas =  8. 9 * 10 ^ 25

To calculate the volume of any gas we should use the ideal gas law equation.

PV = nRT

Here R is the universal gas constant.

To calculate the volume, we need to calculate the number of moles of neon gas. Avogadro's number is used to convert the number of atoms to moles:

1 mole of neon gas = 6.022 * 10^23 atoms of neon gas

The total number of moles of neon gas is:

8.9 * 10^25 atoms / 6.022 * 10^23 atoms/mol = 14.79 mol

Let's assume the temperature is 25°C  = 298 K

The pressure = 1 atm.

The value of R =  0.08206 Latm/(molK).

PV = nRT

V = (NRT) / P

V = (14.79 mol * 0.08206 Latm/(molK) * 298 K) / 1 atm

V = 326.5 L

Therefore we can conclude that the volume of Neon gas is 326.5 L.

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A triglyceride that loses a fatty acid is called a diglyceride or diacylglycerol. This occurs when the triglyceride molecule undergoes a process called hydrolysis.

Hydrolysis breaks the ester bond between one of the fatty acids and the glycerol backbone, releasing a free fatty acid and forming a diglyceride.

This process is essential in the metabolism and digestion of fats in our bodies, as it allows the body to break down complex fat molecules into simpler components that can be absorbed and utilized for energy or other biological functions.

In addition, diglycerides play important roles in cell signaling and membrane structure, serving as essential building blocks for various cellular components.

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Answer:

The answer is D - 3.7 L.

The additional information necessary is: "the half-life of potassium-40." for the scientist to determine the absolute age of the fossil.

Radiometric dating is a method used to determine the absolute age of rocks and fossils based on the decay of radioactive isotopes. The rate of decay of a radioactive isotope is measured in terms of its half-life, which is the time it takes for half of the original parent atoms to decay into daughter atoms.

In this case, the scientist needs to know the half-life of potassium-40 in order to calculate the absolute age of the fossil. By knowing the half-life of potassium-40, the scientist can determine how much time has elapsed since the fossil was formed based on the proportion of parent and daughter atoms present in the fossil.

Therefore, the correct answer is: the half-life of potassium-40.

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If a flexible hot air balloon has a volume of 350,000 L of air at 40 degrees C and 1 atm, 13636 moles of air are in the balloon . This is taken out by ideal gas law.

The ideal gas law, also known as the general gas equation, is the state equation for a hypothetical ideal gas. Although it has several limitations, it is a good approximation of the behavior of many gases under many conditions. Benoît Paul Émile Clapeyron proposed it in 1834 as a combination of empirical Boyle's law, Charles' law, Avogadro's law, and Gay Lussac's law.

using the equation P × V= n × R × T

P = Pressure = 1 atm

V = Volume = 350000 L

n = moles

R = 0.082 L.atm.K⁻¹.mol⁻¹

solving for n ,

moles n =   13636 moles

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true

Explanation:

Atoms cannot be subdivided, created, or destroyed. Atoms of different elements can combine in simple whole number ratios to form chemical compounds.

Answer:

true

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A spontaneous reaction under standard conditions is indicated by the value of K being greater than 1. Thus, the answer to the given question is option C, K = 2.2 x 10².

Standard conditions- Standard conditions are a set of environmental conditions that are considered to be the standard conditions for conducting an experiment. They serve as a reference point to compare the effects of varying environmental conditions on the properties of a substance or the results of an experiment.

Standard conditions in chemistry are considered to be a temperature of 298K (25°C), a pressure of 1 atm (101.3 kPa), and a concentration of 1 mol/L (for solutions).

Spontaneous reaction- A spontaneous reaction is one that proceeds without any external force or intervention. That is, a spontaneous reaction proceeds without the need for energy input from an external source. In other words, it is an exothermic reaction where the products are more stable than the reactants.

The Gibbs free energy change of a spontaneous reaction is negative. The sign of ΔG indicates the spontaneity of a reaction. A negative value indicates that the reaction is spontaneous, whereas a positive value indicates that the reaction is non-spontaneous. The value of ΔG° is used to determine the spontaneity of a reaction under standard conditions.

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To calculate the energy of the photon emitted for Element Y, you can use the following equation:
E = hc/λ
where h is Planck's constant (6.626 x 10-34 Js), c is the speed of light (3 x 108 m/s), and λ is the wavelength of the photon (in meters).

To calculate the wavelength of the photon emitted for Element Y, you can use the following equation:
λ = hc/E
where h is Planck's constant (6.626 x 10-34 Js), c is the speed of light (3 x 108 m/s), and E is the energy of the photon (in Joules)

To calculate the frequency of the photon emitted for Element Y, you can use the following equation:
f = c/λ
where c is the speed of light (3 x 108 m/s), and λ is the wavelength of the photon (in meters).

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The stereocenter-containing molecule is:

1,2-dimethylcyclohexane (both carbons at position 1 and 2 are stereocenters as they have four distinct substituents connected to them)

(both carbons at position 1 and 2 are stereocenters as they have four different substituents attached to them)

Stereocenters are absent from the other compounds that were listed. Because the double bond does not include any substituents that are distinct from one another, the alkene with H wedges and the CH3 dash does not have stereocenters. As all of the carbons in cyclohexane are symmetric and do not have four separate substituents connected to them, the cyclohexane with wedge-dash methyl likewise lacks stereocenters., the only molecule in the list that contains stereocenters is 1,2-dimethylcyclohexane.

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Answer:

oxygen friend

Explanation:

It is generally believed that the Earth's atmosphere did not contain oxygen until around 2500 million years ago (Mya) when oxygen-evolving photosynthetic bacteria arose. At around 800–500 Mya, the oxygen concentration increased sharply to reach the 21% we have today. So, it seems highly likely that life arose as anaerobic organisms, which then evolved to tolerate oxygen and finally, to use it as a terminal acceptor for the energy-producing oxidative processes in the respiration of aerobic bacteria and mitochondria in eukaryotic cells. The respiratory processes employed by typical aerobic organisms today have a wide range of mechanisms to deal with the troublesome side effects of living with a high oxygen concentration.

The reaction involved in the galvanic cell made from a half-cell consisting of a silver electrode in 1 M silver nitrate solution and a half-cell consisting of a zinc electrode in 1 M zinc nitrate is given as follows:2 Ag(s) + Zn2+ (aq) → Zn(s) + 2 Ag+ (aq)The standard cell potential at 25 °C for the given reaction can be determined using the following formula: E°cell

= E°cathode - E°anodeHere, the E°cathode and E°anode represent the standard reduction potentials of cathode and anode respectively. The values of these standard reduction potentials can be obtained from the standard reduction

potentials table.Using the values of standard reduction potentials from the table, we have:E°cell = E°Ag+ / Ag - E°Zn2+ / Zn= +0.80 V - (-0.76 V)= +1.56 VThe reaction is spontaneous at standard conditions because the calculated standard

cell potential is positive (+1.56 V). Therefore, the reaction will proceed spontaneously from left to right direction.The bolded non-consecutive keywords are: spontaneous, standard conditions, galvanic cell, reduction potentials.

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Answer:

7.5g is the mass of potassium nitrate that will dissolve in 25g of water at 20° C?

The answer is 4g. At 20° C, the solubility of potassium nitrate in water is 3.7 g per 100 g of water, which means that about 4 g of potassium nitrate will dissolve in 25 g of water.

Solubility is the ability of a substance to dissolve in a liquid or other solvent. It is a measure of the maximum amount of substance that can be dissolved in a given amount of solvent. Solubility can be affected by factors such as temperature, pressure, and the type of solvent used. In general, the more soluble a substance is, the more easily it will dissolve. Solubility is an important factor in the formulation of many products, such as pharmaceuticals, cosmetics, and food products. It is also used in the manufacture of detergents, paints, and inks. Solubility can be determined experimentally, by measuring the amount of a substance that can be dissolved in a given volume of solvent. The solubility of a substance can also be calculated using equations that take into account the temperature and pressure of the system. Understanding solubility is important for determining the effectiveness of drugs, the shelf life of food products, and the environmental impact of certain chemicals.

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Gamma radiation are the most dangerous type of radioactive emission as they are the most energetic and can penetrate the human body and damage cells. Alpha particles can cause both short-term and long-term health effects, such as cancer.

Out of alpha, beta and gamma radiation, the most dangerous type of radioactive emission is gamma radiation. This is because gamma rays are penetrating, high-energy rays that can easily penetrate the human body and cause damage to cells and DNA. Gamma radiation, unlike alpha and beta radiation, can penetrate the body's skin and tissue, exposing internal organs to radiation. When gamma rays are absorbed by living cells, they can ionize atoms and molecules, causing damage to DNA and other genetic material in the cell. High doses of gamma radiation can cause immediate symptoms such as radiation sickness and even death. Gamma radiation is frequently emitted by unstable radioactive atoms like uranium and plutonium, which are used in nuclear power plants and nuclear weapons. Workers in these industries and anyone exposed to a nuclear accident or bomb are at a higher risk of exposure to gamma radiation. Alpha radiation is a type of ionizing radiation that is emitted by certain types of unstable atoms. Alpha particles are relatively large and have a short range, so they can be stopped by a sheet of paper or the outer layer of human skin. Beta radiation is a type of ionizing radiation that is emitted by certain types of unstable atoms. Beta particles are much smaller than alpha particles, and they can travel through the human body farther than alpha particles. Gamma radiation is a type of electromagnetic radiation, similar to X-rays, but with higher energy and frequency. Gamma rays are produced by the decay of unstable atomic nuclei and are highly penetrating, meaning they can easily pass through solid objects.

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The volume of the balloon at a temperature of 263 K will be approximately 683.1 mL.

Charles's Law states that the volume of a gas is directly proportional to its absolute temperature at constant pressure.

This means that the volume and temperature of a gas are directly proportional to each other as long as the pressure is constant.

It is expressed as:

V₁/T₁ = V₂/T₂

Where V₁  and T₁ are the initial volume and temperature, V₂ is the final volume, and T₂ is the final temperature.

Given that:

Solving for V₂, we get:

V₂ = V₁T₂ / T₁

V₂ = ( 800 × 263 ) / 308

V₂ = 210400 / 308

V₂ = 683.1 mL

Therefore, the volume is  683.1 mL.

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When 0.1 M HCl and 0.1 M NaOH are combined in equal amounts, a process known as neutralisation will take place, producing water and a salt as byproducts.

In a neutralisation process, which takes place when an acid and a base are mixed, the H+ ions from the acid and the OH- ions from the base combine to generate water molecules. In this instance, when 0.1 M HCl and 0.1 M NaOH are combined in equal parts, they will react 1:1 to form water and the salt NaCl. The final mixture's pH will be 7, which is neutral. This is due to the fact that only water and salt are left after the reaction, totally consuming the H+ and OH- ions. A lot of industries, including industry, agriculture, and medicine, utilise this kind of reaction.

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The ionization energy, or ionization potential, is the energy required to completely remove an electron from a gaseous atom or ion. The closer and more tightly bound an electron is to the nucleus, the more difficult it will be to remove, and the higher its ionization energy will be.

I suppose how dazzling the star appear to a meter here on Earth. On the opposing hand, a star's brightness refers to how much light is emitted from its surface.

absolute magnitude: the amount of brightness a star would have at a given distance. The brightness of a galaxy seen from the Earth is known as its apparent magnitude.

Because of this, the sample's name, "apparent" brightness, refers to the brightness of things as seen from our vantage point rather than their actual or "true" brightness. Astronomers must measure a star's luminosity, or absolute brightness, in to understand the precise amount of heat it emits.

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There are 4 chirality centers in an aldohexose. The correct answer is option b.

Aldohexoses are six-carbon monosaccharides with a carbonyl functional group (aldehyde group) and five other carbon atoms, each of which is associated with an alcohol functional group in their straight-chain form. The carbonyl carbon, which is referred to as the anomeric carbon, determines the stereochemistry and the cyclic form of aldohexoses.

Chirality centers are carbon atoms that have four distinct substituents bonded to them, resulting in the ability to exist as stereoisomers. These stereoisomers are mirror images of each other and cannot be superimposed upon each other.Therefore, it is important to count the number of chirality centers present in the aldohexose structure.

There are four chirality centers in aldohexose, which are present at carbon atoms 2, 3, 4, and 5.

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Answer: A and B

Explanation:

i took the test hope it will help --_o