Which of the following is an example of a problem that could be solved using the scientific method?
a. Tire is flat due to a nail
b. Grass is dead due to a drought
c. Water pressure is low due to a leak
d. Apple tree is not producing apples

Answer:

43.4%

Explanation:

A 50.0 mL solution of 0.250 M HC₂H₃O₂ before and after adding 50 mL of 0.250 M NaOH has a pH of 2.87, the pH changes due to the formation of a buffer solution, which can be calculated using the Henderson-Hasselbalch equation.

This problem requires us to calculate the pH of a buffer solution after the addition of a strong base. A buffer solution is one that resists pH changes when modest amounts of acid or base are added. The buffer system in this case is the weak acid, acetic acid (HC₂H₃O₂) and its conjugate base, acetate ion (C₂H₃O₂-).

Before the addition of NaOH, we have a solution of 0.250 M HC₂H₃O₂, which we can assume to be completely dissociated in water:

HC₂H₃O₂ + H₂O ⇌ H₃O+ + C₂H₃O₂-

HC₂H₃O₂ has a Ka value of 1.8 x 10-5. We can use this Ka value to calculate the equilibrium concentration of H3O+ and C₂H₃O₂- in the solution.

First, we need to calculate the initial concentrations of HC₂H₃O₂ and C₂H₃O₂-.

moles of HC₂H₃O₂ = 0.250 M × 0.0500 L = 0.0125 mol

moles of C₂H₃O₂- = 0 mol (since there is no NaOH added yet)

Since HC₂H₃O₂ is a weak acid, it only partially dissociates in water. The equilibrium concentrations of H₃O+ and C₂H₃O₂- can be calculated using the Ka expression:

Ka = [H₃O+][C₂H₃O₂-]/[HC₂H₃O₂]

We can assume that the initial concentration of H3O+ is negligible compared to the amount that will be produced by the dissociation of HC₂H₃O₂, so we can simplify the expression to:

Ka = [H₃O+]²/[HC₂H₃O₂]

[H₃O+]² = Ka × [HC₂H₃O₂]

[H₃O+]² = 1.8 × 10⁻⁵ × 0.0125

[H₃O+] = 1.34 × 10⁻³ M

Now that we know the equilibrium concentration of H₃O+, we can use the pH formula to calculate the pH:

pH = -log[H₃O+]

pH = -log(1.34 × 10⁻³)

pH = 2.87

This is the pH of the buffer solution before the addition of NaOH.

Next, we add 50 mL of 0.250 M NaOH to the solution. NaOH is a strong base, so it completely dissociates in water to produce OH- ions:

NaOH → Na+ + OH-

The OH- ions will react with the acetate ions in the buffer solution to form water and acetate ions:

OH- + C₂H₃O₂- → H₂O + C₂H₃O₂-

This reaction will consume some of the acetate ions in the buffer solution, causing the equilibrium to shift to the left to produce more acetate ions.

To calculate the new concentrations of H₃O+ and C₂H₃O₂-, we need to use the Henderson-Hasselbalch equation:

pH = pKa + log([C₂H₃O₂-]/[HC₂H₃O₂])

where pKa = -log(Ka), [C₂H₃O₂-] is the equilibrium concentration of acetate ions, and [HC₂H₃O₂] is the equilibrium concentration of acetic acid.

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There are approximately \(2.76 * 10^{24\) ammonia molecules in the given sample.

To calculate the number of ammonia molecules in the sample, we need to use Avogadro's number and the molar mass of ammonia.

The molar mass of ammonia \((NH_3)\) can be calculated by adding up the atomic masses of nitrogen (N) and hydrogen (H):

Molar mass of \(NH_3\) = (1 x atomic mass of N) + (3 x atomic mass of H)

              = (1 x 14.01 g/mol) + (3 x 1.01 g/mol)

              = 14.01 g/mol + 3.03 g/mol

              = 17.04 g/mol

Now, we can calculate the number of moles of ammonia in the sample using the formula:

Number of moles = Mass of the sample / Molar mass

Number of moles = 78.25 g / 17.04 g/mol

              ≈ 4.5865 mol (rounded to four decimal places)

Finally, we can use Avogadro's number, which represents the number of particles (atoms, molecules, etc.) in one mole of a substance. Avogadro's number is approximately \(6.022 * 10^{23\) particles/mol.

Number of ammonia molecules = Number of moles x Avogadro's number

Number of ammonia molecules ≈ 4.5865 mol x (\(6.022 * 10^{23\) molecules/mol)

                           ≈ \(2.76 * 10^{24\) molecules (rounded to two significant figures)

Therefore, the provided sample contains roughly \(2.76 * 10^{24\) ammonia molecules.

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The number of ammonia molecules in the sample is approximately 2.764 x \(10^{24}\) molecules.

To calculate the number of ammonia molecules in a given sample, we need to use Avogadro's number and the molar mass of ammonia.

The molar mass of ammonia (NH3) is calculated as follows:

Molar mass of N = 14.01 g/mol

Molar mass of H = 1.01 g/mol

Total molar mass of NH3 = 14.01 g/mol + (3 * 1.01 g/mol) = 17.03 g/mol

Now, we can calculate the number of moles of ammonia in the sample:

Number of moles = Mass of sample / Molar mass of NH3

Number of moles = 78.25 g / 17.03 g/mol = 4.594 moles

Next, we use Avogadro's number, which states that there are 6.022 x \(10^{23}\) molecules in one mole of a substance.

Number of molecules = Number of moles * Avogadro's number

Number of molecules = 4.594 moles * 6.022 x \(10^{23}\) molecules/mol = 2.764 x \(10^{24}\) molecules

Therefore, there are approximately 2.764 x \(10^{24}\) ammonia molecules in the given sample of 78.25 g.

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Answer:

3 grams C₅H₁₀O₅

Explanation:

To find the mass of ribose needed to prepare the sample, you need to

(1) convert the volume from mL to L (1,000 mL = 1 L)

(2) calculate the number of moles (M = moles / L)

(3) convert moles to grams (using the molar mass of ribose)

The molecular formula of ribose is C₅H₁₀O₅. It is important to arrange all of the ratios/conversions in a way that allows for the cancellation of units.

(Step 1)

 200 mL C₅H₁₀O₅                   1 L
----------------------------  x  ----------------------  =  0.2 L C₅H₁₀O₅
                                           1,000 mL

(Step 2)

Molarity (M) = moles / volume (L)                 <----- Molarity ratio

0.1 M = moles / 0.2 L                                     <----- Insert values

0.02 = moles                                                  <----- Multiply both sides by 0.2 L

(Step 3)

Atomic Mass (C): 12.011 g/mol

Atomic Mass (H): 1.008 g/mol

Atomic Mass (O): 15.999 g/mol

Molar Mass (C₅H₁₀O₅): 5(12.011 g/mol) + 10(1.008 g/mol) + 5(15.999 g/mol) = 150.13 g/mol

 0.02 moles C₅H₁₀O₅              150.13 g
----------------------------------  x  -------------------  =  3 grams C₅H₁₀O₅
                                                  1 mole

The periodic table is an ordered way of representing chemical elements. They were ordered according to their atomic number, remember that the atomic number corresponds to the number of protons of the elements.

So the answer will be option C) Atomic Number

The calculated formula masses to 133.5 amu, we find that the substance with a formula mass closest to 133.5 amu is (d) AlCl3. Therefore, the answer is option D.

To identify the substance with a formula mass of 133.5 amu, we need to calculate the formula mass of each given substance and compare it to 133.5 amu.

(a) MgCl2:

The formula mass of MgCl2 can be calculated by adding the atomic masses of magnesium (Mg) and chlorine (Cl).

Mg: atomic mass = 24.31 amu

Cl: atomic mass = 35.45 amu

Formula mass of MgCl2 = (24.31 amu) + 2(35.45 amu) = 95.21 amu

(b) SCl:

The formula mass of SCl can be calculated by adding the atomic masses of sulfur (S) and chlorine (Cl).

S: atomic mass = 32.07 amu

Cl: atomic mass = 35.45 amu

Formula mass of SCl = 32.07 amu + 35.45 amu = 67.52 amu

(c) BCl:

The formula mass of BCl can be calculated by adding the atomic mass of boron (B) and chlorine (Cl).

B: atomic mass = 10.81 amu

Cl: atomic mass = 35.45 amu

Formula mass of BCl = 10.81 amu + 35.45 amu = 46.26 amu

(d) AlCl3:

The formula mass of AlCl3 can be calculated by adding the atomic mass of aluminum (Al) and 3 times the atomic mass of chlorine (Cl).

Al: atomic mass = 26.98 amu

Cl: atomic mass = 35.45 amu

Formula mass of AlCl3 = 26.98 amu + 3(35.45 amu) = 133.78 amu. Option D

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Answer:

fire > rocks > air

The difference between all three Magnesium, Mg isotopes is in; the number of neutrons.

Isotopy is a property of elements in which case the element has two or more types of atoms that have the same atomic number and hence, same position in the periodic table, but differ in nucleon numbers due to different numbers of neutrons in their nuclei.

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173 degrees Celsius is extremely hot and would feel scorching and painful. It is well above the boiling point of water (100 degrees Celsius), so any contact with surfaces at this temperature would cause severe burns.

In more detail, at 173 degrees Celsius, the air would be unbearably hot, making it difficult to breathe. Your skin would feel a burning sensation immediately upon contact with any object or surface heated to this temperature. It would be similar to touching a hot stove or a blazing fire. The intense heat would quickly penetrate your skin, causing deep burns and potentially permanent damage. Extreme caution and protective measures are necessary to avoid such high temperatures, as they pose a significant risk to health and safety. It is important to stay away from such extreme temperatures to prevent serious harm.

In summary, 173 degrees Celsius would feel extremely hot and would cause severe burns upon contact with objects or surfaces at this temperature. The air would be scorching and difficult to breathe, making it essential to avoid exposure to such extreme heat for the sake of personal safety.

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Some acids can produce painful burns and damage tissues.

Acids can react violently with water and are harmful if water gets in the mouth eyes or near other aqueous solutions. Vapors from some acids are water soluble and can damage the eyes nasal passages throat, and lungs. Acid burns are usually felt immediately.

The short answer is that both acids and bases can be dangerous depending on pH and strength. For example, strong acids are more dangerous than weak bases and vice versa. Acids and bases are highly reactive with these chemicals and on contact form salts that destroy the original ingredients and damage the skin. Another major reason is that strong acids and strong bases quickly dissociate upon contact with water.

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Answer:

A chemical change

Explanation:

A chemical change is a change that produces matter with a different composition than the original matter

16 fluid ounce bottle of witch hazel will have 66.24ml of ethyl alcohol.

volume percent of a solution is the ratio of the volume of a solute present in a solution to the volume of the solution as a whole.

Volume Percent  =  V solute(mL)/V solution(mL)  ×  100

Volume Percent  =  V solute(mL)/V solute(mL)+V solvent(mL)  ×  100

14% of 16 fluid ounce

=(14/100)×16

=0.14×16

=2.24 fluid ounce

=66.24ml

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Calcium (Ca) is in group 2 and period 4 on the periodic table be because Calcium has 2 valence electrons and 4 electron shell. Thus, calcium is a metal like all other group 2 element.

The correct answer to the question is Option C. Calcium, like all group 2 elements, is reactive and a solid at room temperature.

Calcium is a group 2 element majorly because it has 2 valence electrons. It is also in period 4 because it has 4 electron shells.

Being a group 2 element, calcium is a solid at room temperature and also reactive. All elements in the group 2 are metals.

There are other elements in period 4 which are not solid. For example krypton is an element in period 4 and it is a gas and not reactive.

From the above information, we can conclude that the correct answer to the question is:

Option C. Calcium, like all group 2 elements, is reactive and a solid at room temperature.

See attached image

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Answer:

Mg-9

N-6

C-2

O-4

Ca-9

P-6

O-24

Explanation:

Answer:

Reaction rate

Explanation:

We are told that Ben observes how quickly some dry wood is burning in a campfire.

This is an example of reaction rate because it tells us the speed i.e. how fast the dry wood is reacting with the camp fire.

Answer:

\(Q=-126.1kJ\)

Explanation:

Hello,

In this case, by means of the released heat, we need to consider the cooling of water in two steps:

1. Condensation of steam at 100 °C.

2. Cooling of water from 100 °C to 37 °C.

Therefore, we need the enthalpy of condensation of water that is 40.65 2258.33 J/g and the specific heat that is 4.18 J/g°C for the same amount of cooled water to obtain:

\(Q=50.0g*[-2258.33\frac{J}{g}+4.18\frac{J}{g\°C}(37-100)\°C]\\\\Q=-126.1kJ\)

Best regards.

Answer:

a power plant that runs on oil

Explanation:

A generator a power plant that runs on oil uses non-renewable sources of energy to generate electricity.

Non - renewable energy is an energy source that cannot be replenished within a short period of time. It takes geologic time scales to form such energy sources.

Oil is a fossil fuel and a non-renewable source of energy.

As it is used, the reserve is being depleted.

Answer:

a power plant that runs on oil

Answer:

A change is called irreversible if it cannot be changed back again. For example you cannot change a cake back into its ingredients again. Irreversible changes are permanent.

Explanation:

Hope this helps!! :))

One mole of radiant energy will supply 6.02 x 10^23 photons.

The number of photons is calculated by dividing the overall energy of a pulse by the energy of one photon included inside the pulse.

As a result, an electromagnetic energy particle is known as a photon. Photons have no mass, thus they move at the same rate as light.

we need to first calculate the total energy in one mole of photons,

By combining the energy per photon with Avogadro's number (6.022 x 1023), one may determine the energy of a mole of photons:

Energy per mole of photons = Energy per photon x Avogadro's number

we can calculate the energy per mole of photons:

Energy per mole of photons = 3.37 × 10−19 J x 6.022 x 10^23

Energy per mole of photons = 2.03 x 10^5 J/mol

Number of photons in one mole = Energy per mole of photons / Energy per photon

Number of photons in one mole = 2.03 x 10^5 J/mol / 3.37 × 10−19 J

Number of photons in one mole = 6.02 x 10^23 photons/mol

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The answer responses to  the structures shown in the diagram are:

A. chromosomes

C. They would be the same.

B. They are in pairs because each one comes from a different parent.

The chromosomes are in pairs because humans have a diploid number of chromosomes, meaning they have two sets of chromosomes, one inherited from each parent.

The nucleus is important in eukaryotic cells and has many important parts that help the cell work properly. There are some parts inside cells called the nuclear membrane, nucleoplasm, nucleolus, and chromatin. Chromatin is made up of DNA and other proteins.

Every part of a person's body has the same genes, but the way they are organized can be different in different types of cells. The chromosomes in our skin cells might not be the same as the chromosomes in our muscle cells, even if they come from the same person.

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Identify the structures shown.

A. chromosomes

B. mitochondria

C. nuclei

D. vacuoles

C

Describe how the structures from this cell would compare to the structures in the nucleus of another body cell from the same person.

A. There would be longer.

B. They would be shorter.

C. They would be the same.

D. They would be different.

Describe how the structures from this cell would compare to the structures in the nucleus of another body cell from the same person.

A. There would be longer.

B. They would be shorter.

C. They would be the same.

D. They would be different.

Explain why the structures are in pairs.

A. They aren't in pairs.

B. They are in pairs because each one comes from a different parent.

C. This cell is making a copy of itself.

D. The cell always has 2 copies in case 1 is damaged.

Based on the given information, it is not possible to accurately predict which number is the predicted yield, the actual yield, and the percent yield without additional information or context. The percent yield is calculated by comparing the actual yield to the predicted yield, which are both typically measured in grams or moles.

The list of the factors that will increase the reaction rate of a chemical reaction are

The Factors that can increase the reaction rate of a chemical reaction include:

Lastly, Increasing the surface area of the reactants: as the surface area of the reactants increases, the number of reactant particles in contact with each other increases, making it more likely for them to collide and react.

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Answer:

A).

ΔH is positive, Therefore reaction is endothermic

B).

ΔG = ΔH - T∙ΔS

= 98.4 kJ/mol - 300K ∙ 0.09564 kJ/molK

= 69.7 kJ/mol

C).

ΔG is positive, Therefore reaction is non-spontaneous

Explanation:

look i know that its not a drawing but its the best that i can do with what i have. i hope this helps!

Answer:

176

Explanation:

M1V1 =M2V2

200 X 0.880

Answer:

a. Boron trifluoride

b. Propane

c. Dinitrogen pentoxide

d. Carbon Dioxide

e. Silicon Octafluroride?

Explanation:

Glad to help :)

1. The % concentration is 20.7% and the molar concentration, Cm, is 1.5 M.

2. 7.8 grams of potassium sulfate will be formed.

3. 10.7 grams of ammonium chloride will be formed.

4. The volume of hydrogen gas that will be produced is 3.86 liters.

5. 21.43 grams of the 70% acetic acid is needed to prepare 500 grams of 3% acetic acid solution.

1. Mass of potassium sulfate = 1.5 moles * (174.26 g/mol) = 261.39 g

Mass of water (H₂O) = 1000 g

% = (mass of solute/mass of solution) x 100

% = (261.39 g / (261.39 g + 1000 g)) x 100

% ≈ 20.7%

Cm = moles of solute / volume of solution

Moles of potassium sulfate (K2SO4) = 1.5 moles

Volume of water (H2O) = 1000 g / (density of water) = 1000 g / 1 g/mL = 1000 mL = 1 L

Cm = 1.5 moles / 1 L

Cm = 1.5 M

2. The balanced equation for the reaction is:

H₂SO₄ + 2 KOH → K₂SO₄ + 2 H₂O

Molar mass of sulfuric acid (H₂SO₄) = 98.09 g/mol

Moles of sulfuric acid = 10 g / 98.09 g/mol

Moles of sulfuric acid = 0.102 mol

Based on the mole ratio of the reaction, 0.102 moles of sulfuric acid will react to form 0.102 moles of potassium sulfate.

Molar mass of potassium sulfate = 174.26 g/mol

Mass of potassium sulfate = 0.102 mol x 174.26 g/mol

Mass of potassium sulfate ≈ 17.8 g

3. The balanced equation for the reaction is:

Molar mass of hydrochloric acid (HCl) = 36.46 g/mol

Moles of hydrochloric acid (HCl) = 7.3 g / 36.46 g/mol

Moles of hydrochloric acid ≈ 0.2 mol

Based on the mole ratio of the reaction, 0.2 moles of hydrochloric acid will react to form 0.2 moles of ammonium chloride.

Molar mass of ammonium chloride (NH₄Cl) = 53.49 g/mol

Mass of ammonium chloride = 0.2 mol x 53.49 g/mol

Mass of ammonium chloride ≈ 10.7 g

4. The balanced equation for the reaction is:

Molar mass of zinc (Zn) = 65.38 g/mol

Moles of zinc = 13 g / 65.38 g/mol

Moles of zinc ≈ 0.199 mol

Based on the mole ratio of the reaction, 0.199 moles of zinc will react to produce 0.199 moles of hydrogen gas.

Volume of sulfuric acid = 30 g / (density of H₂SO₄ )

The density of H₂SO₄ is 1.84 g/mL

Volume of sulfuric acid  = 30 g / 1.84 g/mL

Volume of sulfuric acid ≈ 16.3 mL or 0.0163 L

Using the ideal gas law, the volume of hydrogen gas produced will be:

V = nRT / P

V = (0.199 mol)(0.0821 L·atm/(mol·K))(273 K) / (1 atm)

V ≈ 3.86 L

5. Assuming that the concentrated original solution of acetic acid is 100% acetic acid (CH₃COOH).

Mass of acetic acid = 500 g x (3/100) = 15 g

The concentrated original solution, however, is 70% acetic acid.

70% acetic acid (mass) = 100% acetic acid (unknown mass)

0.7 * (unknown mass) = 15 g

Solving for the unknown mass:

unknown mass = 15 g / 0.7

unknown mass ≈ 21.43 g

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