Which statement best explains why the atomic theory developed efficiently?
Scientists ignored all previous knowledge about atoms.
Scientists had used creativity and the scientific method in their investigations.
Scientists had used a philosophical viewpoint as a method of investigation.
Scientists rarely repeated experiments to make sure the results were correct.

The reaction occurs via a nucleophilic substitution mechanism. The D_2O molecule acts as the nucleophile, attacking the carbon atom of the CH_3CH_2OBH_3 molecule.

Step 1:

NaBH_4 + CH_3CH_2OH → CH_3CH_2OBH_3 + NaOH

Step 2:

CH_3CH_2OBH_3 + D_2O → CH_3CH_2OD + BH_3OH

Step by explanation in  detail

Step 1:

NaBH_4 + CH_3CH_2OH → CH_3CH_2OBH_3 + NaOH

The reaction occurs via a nucleophilic substitution mechanism. The Na^+ cation acts as a spectator ion and does not take part in the reaction. The BH_4- anion acts as the nucleophile, attacking the carbon atom of the CH_3CH_2OH molecule. This causes the C-O bond to break and the BH_3 group to form a bond with the carbon atom. This results in the formation of the CH_3CH_2OBH_3 molecule and the NaOH molecule.

Step 2:

CH_3CH_2OBH_3 + D_2O → CH_3CH_2OD + BH_3OH

The reaction occurs via a nucleophilic substitution mechanism. The D_2O molecule acts as the nucleophile, attacking the carbon atom of the CH_3CH_2OBH_3 molecule. This causes the C-B bond to break and the D atom to form a bond with the carbon atom. This results in the formation of the CH_3CH_2OD molecule and the BH_3OH molecule.

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A conjugate base solution with a pH between 8 and 10 has little buffer capacity, however at higher pHs, the strong base's presence begins to matter more.

Because of the large concentration of H + cations, a pure acetic acid solution with a pH below 3 already has a pH that is resistant to changes. This is because the concentration of the capacity is so high that it is unaffected by changes in the equilibrium of the solution brought on by the concentration of other ions. Why is a buffer more effective if its pKa is close to the pH? Why does a buffer function best when pH and pKa are equal? Why does increasing the pH by a basic or an acid.

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There are 20 grams of Sodium hydroxide in a molar solution that has a volume of 500 cm3.

Caustic soda and lye are two other names for sodium hydroxide. It is a typical component of soaps and cleansers. Sodium hydroxide seems to be a white, unscented solid at room temperature. Sodium hydroxide is a colorless, odorless liquid. Strong acids and water can cause explosive reactions with it.

Molarity is calculated by

moles (solute) / volume of solution in L

No. of moles = mass / molar mass

We have to find mass of sodium hydroxide (NaOH)

As we know, in 1 L (1000 cm³) of molar solution there is 40 gram of NaOH present.

From using this statement, 500 cm³ of a molar solution, means half liter of a molar solution contain -

= 40 / 2

= 20 gram of NaOH.

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When we work with a chemical that emits hazardous vapors or fumes, the  best way to protect ourself is by using the fumes hood when working with chemicals.

The best way to protect ourself from the chemical fumes or vapor is the work with chemicals in the fumes hood. the fume hood is the ventilation device that limits the exposure of the hazardous fumes or the vapors.

There are several other ways to protect ourself from the chemical fumes are :

These are the some methods use to protect ourself from the chemical fumes or vapors.

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Compared to safety standards, that would be too little chlorine:

10,000 gallons is five times as much water as 2,000.

Therefore, Park's pool needs five times as much chlorine as is required for 2,000 gallons to meet safety regulations.

5 times 3 pills of chlorine equals 15 tablets. For Mark to meet safety standards, 15 chlorine tablets would be required. Use one three-inch tablet for every 10,000 gallons of pool water rather than stuffing your chlorinator or floater to the brim with tablets. This quantity of pills should be sufficient to maintain a good chlorine level if you shock your water once a week.

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Combination reaction: 8 Cu + S8 8 CuS in terms of chemistry. There are multiple reactants and multiple products.

Combination reactions occur when two or more substances combine to form a single new substance. Composite processes are also referred to as synthetic reactions. The typical structure of an active components is A+BAB. A combination reaction occurs when two components combine to form a compound.

A combination synthesis can involve any number of different reactants. A non-metal and a metal combinations reaction every time leads to an electrolytic process. Combination conformational changes fall into one of three categories. In particular, they consist of two elements combined, two compounds combined, and one element combined with one compound.

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He is not falling nor about to fall which means he’s perfectly balanced. So this means the force in the photo and friction in this photo is in a balanced condition, balancing the boy.

In the given picture, the applied force and the force of friction are balanced. if two forces act in the direction to make the object in a balanced state.

If the forces are in a balanced state it does not change the motion of the object, and if it is in an unbalanced state, it causes to change in the state of the motion.

Therefore, the force of friction and the gravitational force are balanced is the correct option.

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The given question is incomplete, so the complete question image is attached in the image below.

The amount of energy used to heat the water from 0°C to 70°C is 8,786.4J.

The amount of energy used in heating a substance can be calculated using the following formula:

Q = mc∆T

Where;

According to this question, a student heated 30 milliliters of water from 0 degrees celsius to 70 degrees celsius.

Since 1mL of pure water equals 1 gram, then 30mL of water will equal 30grams of water.

Q = 30 × 4.184 × (70 - 0)

Q = 8,786.4J

Therefore, 8,786.4J is the energy used to heat the water sample.

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Taking into account the definition of molarity,  the molarity of a solution made up of 15.5 mol of ammonium sulfate dissolved in enough water to make 45 liters of solution is 0.34 moles/L.

The molar concentration is a measure of the concentration of a solute in a solution, be it some molecular, ionic or atomic species and indicates the number of moles of solute contained in one liter of solution.

The molarity of a solution is calculated by:

molarity= number of moles÷ volume

Molarity is expressed in units moles/L.

In this case, you have:

Replacing in the definition of molarity:

molarity= 15.5 moles÷ 45 L

Solving:

molarity= 0.34 moles/L

Finally, the molarity of the solution is 0.34 moles/L.

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After 4 minutes, 200 g of protactinium-234 would remain.

Protactinium-234 is a radioactive isotope of protactinium. It is a fission product that is produced when uranium atoms undergo fission. It has a half-life of 1.17 minutes and decays via beta-decay to uranium-234. It is the most stable isotope of protactinium and is found in very small quantities in uranium ore. The main uses for protactinium-234 are for research, nuclear medicine and nuclear power. In research, it can be used to study properties of fission products and to measure the efficiency of nuclear reactors. In nuclear medicine, it can be used to detect cancers and other conditions. Finally, it can be used in nuclear power plants to help regulate and control the flow of energy.

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Nitrophenols should be in the following order: para - > ortho - > meta -. There is one additional resonance structure in ortho- and para-nitrophenol.

The stability of the conjugate base dictates the acidity of nitrophenols (or any acid, for that matter). By examining the resonance structures, it is possible to assess the relative stability of m- and p-nitrophenols.Therefore, ortho- and para-nitrophenol are both more acidic than meta-nitrophenol as a result of resonance effects.Sort the following substances in ascending order of acidity: One is ortho-nitrophenol. Paranitrophenol 2. Para-methylphenol 3. 4 Nitrocyclohexanol An intermediary in the creation of paracetamol is 4-nitrophenol. It is then acetylated with acetic anhydride after being reduced to 4-aminophenol.

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Answer:

Hey there! The nuclear symbol for an ion with a charge of +220 protons and 24 neutrons would be written as follows:

220+ 24

The symbol consists of two parts: the atomic number (220+) and the atomic mass (24). The atomic number is the number of protons in the nucleus of an atom, and it is represented by a superscript on the left side of the symbol. The atomic mass is the total number of protons and neutrons in the nucleus, and it is represented by a subscript on the right side of the symbol.

In this case, the atomic number of the ion is 220, which indicates that it has 220 protons in its nucleus. The atomic mass is 24, which indicates that it has a total of 220 protons + 24 neutrons = 244 particles in its nucleus.

________________________________________________________

Nuclear symbols are a way of writing down the important information about atoms and ions in a short and easy-to-read format. They usually consist of two parts: the atomic number and the atomic mass. The atomic number tells us how many protons an atom has in its nucleus, and the atomic mass tells us the total number of protons and neutrons. For example, the nuclear symbol for carbon is 6 12C, which tells us that carbon has 6 protons and 12 particles (6 protons + 6 neutrons) in its nucleus.

To determine the number of protons in an atom or ion, we can look at its atomic number, which is usually written as a superscript on the left side of the nuclear symbol. For example, if the nuclear symbol for an atom or ion is written as 6 12C, we can tell that it has 6 protons. To determine the number of neutrons, we can subtract the atomic number from the atomic mass. For example, if the atomic mass is 12 and the atomic number is 6, then the number of neutrons is 12 - 6 = 6. To determine the number of electrons, we can just look at the overall charge of the atom or ion. If it is neutral, then it will have the same number of protons and electrons. If it is positive or negative, then it will have more or fewer electrons than protons, respectively.

The block has a density of 7.3 g/ml. The density is the same as for tin. Tin is the metal's true identity.

Absolute population and particle density are the two main types of density. Relative density, also called as coarse aggregate, is the ratio of a substance's density to the volume of a reference substance. The reference substance is often water.

The density of a substance is a measurement of its thickness in relation to its volume. A product will float in a solution if its density is lower than the water's, while it will sink if it has a higher density.

Density of the block can be calculate as follows:

Volume of metal = 1xb×h

I = 0.5839 in

b = 0.531 in

h = 0.4981 in

volume = 0.5839×0.531×0.4981

=0.1544363

=2.53ml

mass of metal =1.84×10⁴ mg

=18.4 g

density = g/ml

=18.4/2.53

=7.3 g/ml

from its density we can conclude the block of metal is Tin

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The conservation of natural resources be most effective in reducing carbon dioxide in the atmosphere,  is the planting more trees.

The planting the more new tress is the one of the most effective ways to reduce the atmospheric carbon dioxide. this will also limits the global warming. the plants remove the carbon dioxide from the atmosphere through the photosynthesis. plants helps to stop the climate change as they will remove the carbon dioxide from the atmosphere. and  store the carbon in tress and the soil.

Thus , the way to reduce the carbon dioxide from the atmosphere is the planting more and more trees.

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Since lead has a density of 11.53 g/cm^3, the volume of a 0.255 pound sample of lead is equal to 10.03 cm³.

In Science, the density of a chemical substance such as lead can be calculated by using this formula:

Density = M/V

Where:

Next, we would convert the value of the mass in pound to grams by multiplying it by 453.6 as follows;

Mass = 0.255 × 453.6

Mass = 115.668 grams

Making volume the subject of formula, we have:

Volume = Mass/Density

Volume = 115.668/11.53

Volume = 10.03 cm³.

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H2SO3, or sulfuric acid, is a compound that behaves as an acid when dissolved in water. The other compounds listed are either bases, alkanes, or ethers and are not acidic when dissolved in water.

H2SO3, or sulfuric acid, is a compound that behaves as an acid when dissolved in water. Acids are compounds that donate protons when dissolved in aqueous solutions, and sulfuric acid is one of the most common acids used in aqueous solutions. Other compounds listed, such as CH3OCH3, KOH, and CH4, are not acids when dissolved in water. CH3OCH3 is an ether, KOH is a base, and CH4 is an alkane. Acids will typically have a pH value less than 7, while bases have a pH greater than 7. H2SO3 is a strong acid with a pH value of around 1, making it the only compound listed that behaves as an acid when dissolved in water.

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The unit of f''(a) is milliliters/minute^2

The function t=f(a) models the time, in minutes, for a chemical reaction to occur as a function of the amount a of catalyst used, measured in milliliters.

So, here double differentiation is to be done.

t=f(a)

differentiating with respect to t,

d(t)/dt = d(f'(a))/dt

or, d(f'(a))/dt = 1

again differentiating with respect to t,

d [d(f'(a))/dt]/dt = d(1)/dt = 0 ...1

or, f''(a) = 0

so, here if we put 'unit expression' in Left hand side of 1

it is d [d(f'(a))/dt]/dt  i.e.  mililiters/miniute/minute [as given t is measured in minute and f(a) is measured in ml)

or, ml/minute^2

so as we are performing double differentiation, the unit of f''(a) is milliliters/minute^2

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The order of decreasing bond angle for the given molecules is :

O OF2 > NH3 > CCl4 > CO2

In molecules with a central atom, the bond angle is determined by the electron pair-bond pair repulsion. The bond angle decreases as the number of electron pair-bond pair increases. In OF2 the central atom is O, and it has 2 lone pairs and 2 single bonds, the bond angle is expected to be smaller than in the other molecules.In NH3, the central atom is N, and it has 3 single bonds and 1 lone pair, the bond angle is expected to be larger than in OF2 but smaller than in CO2 and CCl4. In CO2 and CCl4, the central atoms are C and Cl respectively, and they have 4 single bonds and no lone pairs, the bond angle is expected to be larger than in NH3, but smaller than in OF2.

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A substance has 0. 0152088 moles per 10 grammes. One can use the equation grams = weight / molar mass to determine this. The volume of one mole of a chemical is represented by its molar mass on the chemical elements.

You would take its weight (10g) and multiply it by the material's molar mass to determine the number of molecules within 10g of a substance. For instance, if the material is water, its molar mass is 18. 015 g/mol, meaning that 10 g is comparable to 0. 555 molecules of water.

However, the formula moles = mass / molar weight can be used to determine the number of moles in an unit weight regardless of the substance. Therefore, there are 0. 0152088 mole in 10

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According to stoichiometry and STP conditions ,1785.90 liters of hydrogen is produced.

It is the determination of proportions of elements or compounds in a chemical reaction. The related relations are based on law of conservation of mass and law of combining weights and volumes.

Stoichiometry is used in quantitative analysis for measuring concentrations of substances present in the sample.

In the given reaction as per stoichiometry, 149.84 g of As produces 6 g hydrogen , thus, 39.3 g of As will produce 39.3×6/149.84=1.573 g.

As per STP conditions, V=1.573/2×8.314×273/1=1785.90 liters.

Thus, 1785.90 liters of hydrogen is produced.

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To solve this we must be knowing each and every concept related to mutation and types of mutations. Therefore, the correct option is option C.

A mutation is, at its most basic, a change or alteration. Chromosome and gene alterations, known as mutations in biology, frequently appear physically.

One grizzly bear population has moved to an area that has snow year-round. If a mutation for coat color is going to spread through the population then Grizzly bears that have a lighter fur mutation can catch prey more easily and so have more resources to have more offspring. Due to this, the trait starts to spread through the population.

Therefore, the correct option is option C.

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The atomic number of Potassium(K) is 19

Knowing the number of electrons in the K atom is necessary before we can write the potassium(K) electron configuration.

There are 19 electrons. All 19 electrons will be positioned in orbitals surrounding the nucleus of the potassium(k) atom when the configuration is written.

there are some steps:

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Answer: devide the concept

Explanation: devide and then answer it

0.0080 grams are in 0.89 moles of CaCI₂.

The mole (M) is defined as it contain exactly 6.023 × 10²³ elementary entities present in it. 1 mole is exactly equal to the 6.023 × 10²³ elementary entities.

We can solve the above problem as follows;

So,

1 Mole of substance = Molar mass of the substance.

The given compound named is Calcium Chloride.

Then,

Molar mass of Calcium chloride = 1 mole

Molar mass of CaCl₂ = 40 + 2 × 35.4

= 110.9g/mol

Therefore,

110.9 grams of CaCl₂ = 1 mole

1 gram of CaCl₂ = 1 / 110.9

0.89 grams of CaCl₂

= 1 / 110 ×  0.89

= 0.0080 grams

Thus, 0.0080 grams are in 0.89 moles of CaCI₂.

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The rate constant of the reaction is 0.56 M⁻¹s⁻¹. The time required to change the concentration of the reactant from 0.900 to 0.100 M is 15.87s.

The half-life of a reaction can be defined as the time needed for a reactant to reach one-half of its initial concentration. For a 1st-order reaction, the half-life is independent of concentration and constant with time.

The half-life period of the second-order reaction can be written as:

[tex]\displaystyle t_{1/2} =\frac{1}{k[A]_o}[/tex]

Given the half-life of the reaction = 2.00 s

The initial concentration of [NOBr]₀ = 0.900 M

The rate constant of the reaction, k = 1/2 ×0.900 = 0.56 M⁻¹s⁻¹

The time required to change concentration from 0.900 to 0.100 M is:

[tex]\displaystyle kt =\frac{1}{[A]} -\frac{1}{[A]_o}[/tex]

0.56 ×t = 1/0.1 -1/0.9

t = 15.87 s

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First, we must compute the index of hydrogen deficiency, IHD, using the molecular formula of the compound [tex]C_{10}H_{14}O_{2}[/tex].

What is a spectrum data?

Spectrum data is data collected from spectroscopic experiments, which measure the interaction of matter with electromagnetic radiation. This data can be used to identify the chemical composition of a sample, as different elements and molecules absorb and emit radiation at different wavelengths.

Then, number of C atoms - [tex]\frac{number of atoms}{2} + 1[/tex]

                                          = [tex]10 + \frac{14}{2} + 1[/tex]

                                          = [tex]10 - 7 + 1[/tex]

                                          = [tex]4[/tex]

Based on the molecular structure, this tells us how many multiple bonds and rings the compound has.

This compound contains four unsaturated bonds. We can tell from the spectrum data that it is aromatic (chemical shifts above 6 comes from aromatic protons). Based on this, we can conclude that the structure of this compound contains a benzene ring. Four IHD are found in the benzene ring, one from the ring and three from double bonds.

Following that, IR spectrum data revealed that absorption on [tex]3150-2850 cm^{-1}[/tex] indicated hybridised CH bonds.

The following chemical shifts are observed in the NMR spectrum data:

On 1,4ppm, it becomes a 6H triplet. It has two protons in its neighbourhood because it is a triplet, and it comes from [tex]CH_{3}(1)[/tex]. This group must be linked to the [tex]CH_{2}(2)[/tex].

A quartet on 4,0ppm, belongs to 4H from [tex]CH_{2}(2)[/tex].  It has 3 protons in neighborhood stop it it attached to the [tex]CH_{3}(1)[/tex] and singlet on 6,8ppm comes of aromatic protons, 4H (3).

Based on the [tex]^{1} HNMR[/tex] spectrum data, we can only attach the two O atoms to the benzene ring and the [tex]CH_{2}(2)[/tex] group.

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A double replacement reaction will occur is a precipitate is formed, or a gas is formed, or a solvent is formed.

Solvent is a substance that is capable of dissolving other substances, resulting in a homogeneous mixture. Solvents are used in many industrial and household processes, including cleaning, extraction, and purification. Common solvents include water, alcohols, ketones, acids, and bases. Solvents can be used to dissolve both organic and inorganic substances. They are often used to separate mixtures of different substances, as well as to dissolve and purify them. Some solvents are miscible with one another, while others are not. Solvents can also be used to dissolve and disperse solids in a liquid.

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30% of the original amount of mixture evaporated during the 10-day period.

In order to determine the percentage of the original amount of mixture that evaporated during the 10-day period, we need to first determine how much water and how much liquid chemical were present in the beaker initially.

Given that the ratio of water to liquid chemical is 3:5, we can assume that the total number of parts is 8 (3+5).

So, the original amount of water is 3 parts / 8 parts = 0.375

And the original amount of liquid chemical is 5 parts / 8 parts = 0.625

We can then use this information to determine how much of each substance evaporated each day:

2% of 40 L of water = 0.02 x 40 L = 0.8 L

5% of 40 L of liquid chemical = 0.05 x 40 L = 2 L

We can then add up the total amount of each substance that evaporated over the 10 days to find the total amount that evaporated from the beaker:

0.8 L of water evaporated/day x 10 days = 8 L

2 L of liquid chemical evaporated/day x 10 days = 20 L

Finally, we can add up the total amount of each substance that evaporated and divide by the total amount of the original mixture to find the percentage of the original amount that evaporated:

(8 L + 20 L) / (40 L + 40 L) = 0.3 or 30%

So 30% of the original amount of mixture evaporated during the 10-day period.

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