Which of the following is evidence that
a chemical change has occurred?

a. Water bubbling when it starts to boil.

b. Detergent removing grease from a dish.

c. Sugar turning black when it burns.

d. Oil and vinegar separating in salad
dressing

we would need 2625.13 grams (or 2.62513 kilograms) of NaCl.

To calculate the mass of NaCl required to produce a 26.4 mol/L solution with a 1.7 L volume, we need to use the formula that relates the mass of solute, moles of solute, and molarity:Molarity (M) = moles of solute / liters of solution Rearranging this formula, we get:moles of solute = Molarity (M) x liters of solutionWe can use this formula to find the moles of NaCl needed:moles of NaCl = 26.4 mol/L x 1.7 L = 44.88 molNow, we can use the molar mass of NaCl to convert from moles to grams. The molar mass of NaCl is 58.44 g/mol:mass of NaCl = moles of NaCl x molar mass of NaClmass of NaCl = 44.88 mol x 58.44 g/mol = 2625.13 gTo produce a 26.4 mol/L solution with a 1.7 L volume.

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Answer:

D

Explanation:

The correct answer is D. In ethylene (CH2=CH2), the carbon atoms in the double bond have two unhybridized p-orbitals.

Oxygen-16: 8 protons, 8 neutrons, 8 electrons

Oxygen-18: 8 protons, 10 neutrons, 8 electrons

Using atomic and mass numbers, we can find information about the makeup of atoms.

Protons

Every element has a unique number of protons, and every atom of the same element will have the same number of protons. This means that both oxygen atoms must have the same number of protons. The number of protons in an element is equal to its atomic number. Since oxygen has an atomic number of 8, all oxygen atoms will have 8 protons. This means that oxygen-16 and oxygen-18 have 8 protons.

Neutrons

The number of neutrons an atom of a certain element can have varies. Atoms of the same element that have different numbers of neutrons are known as isotopes. The number of neutrons can be found through the mass number. The mass number is the number that follows the dash in the name of the isotope. This number is equal to the protons plus the neutrons. So, to find the number of neutrons in an oxygen atom, subtract 8 protons from the mass number. This means oxygen-16 has 8 neutrons and oxygen-18 has 10 neutrons.

Electrons

Remember that electrons are negatively charged, protons are positively charged, and neutrons have no charge. The number of electrons in an atom determines the charge of the atom. If the number of electrons equals the number of protons, then the charge of the atom will equal 0. If there are more electrons, then the atom will be negatively charged and vice versa. Since neither of the atoms has any indication of a nonzero charge, the number of electrons must equal the number of protons. So, both oxygen atoms have 8 electrons.

This question is asking for a method for the determination of the freezing point in a solution that does not have a noticeable transition in the cooling curve, which is basically based on a linear fit method.

The first step, would be to understand that when the transition is well-defined as the one on the attached file, we can just identify the temperature by just reading the value on the graph, at the time the slope has a pronounced change. For instance, on the attached, the transition occurs after about 43 seconds and the freezing point will be about 4 °C.

However, when we cannot identify a pronounced change in the slope, it will be necessary to use a linear fit method (such as minimum squares) to figure out the equation for each segmented line having a significantly different slope and then equal them so that we can numerically solve for the intercept.

As an example, imagine two of the segmented lines have the following equations after applying the linear fit method:

\(y=-3.5 x + 25\\\\y=-0.52 x + 2\)

First of all, we equal them to find the x-value, in this case the time at which the freezing point takes place:

\(-3.5 x + 25=-0.52 x + 2\\\\-3.5 x+0.52 x =2-25\\\\x=\frac{-23}{-2.98}=7.72\)

Next, we plug it in in any of the trendlines to obtain the freezing point as the y-value:

\(y=-3.5 (7.72) + 25\\\\y = 1.84\)

This means the freezing point takes place after 7.72 second of cooling and is about 1.84 °C. Now you can replicate it for any not well-defined cooling curve.

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The student's method for preparing pure crystals of copper sulfate contains errors and does not produce the desired outcome.

Use copper oxide instead of calcium carbonate: The student should add copper oxide (CuO) to the hydrochloric acid instead of calcium carbonate. Copper oxide reacts with hydrochloric acid to form copper chloride, which can then be converted to copper sulfate through a subsequent reaction with sulfuric acid.

Add sulfuric acid to the copper chloride solution: After the copper chloride solution is formed, the student should add sulfuric acid to it. This reaction between copper chloride and sulfuric acid will yield copper sulfate and hydrochloric acid. The student should ensure that the correct stoichiometric ratio is maintained to maximize the yield of copper sulfate crystals.

Crystal formation: The student should allow the solution to cool slowly after the reaction with sulfuric acid. This promotes the formation of larger, well-defined copper sulfate crystals.

Filtration and drying: Once the crystals have formed, the student should filter the solution to separate the solid crystals from the remaining liquid. The filtered crystals should then be thoroughly dried to remove any remaining water, resulting in pure copper sulfate crystals.

By following these improvements, the student can obtain pure crystals of copper sulfate.

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The order of boiling point from the highest to the lowest from the given compounds above are as follows:

CH3CH2CH2CH2CH2OH - CH3CH2CH2CH2CH2Br - CH3CH2CH2CH2CH3 - CH3CH2CH3.

The correct order is option b, d, c and a.

The boiling point of substances can simply be defined as that temperature at which liquids boils and then change to vapor or steam.

However, from the above given task, the organic compound, CH3CH2CH2CH2CH2OH has the same boiling simply because of its power to participate in hydrogen bond formation. This compound CH3CH2CH2CH2CH2OH is known as 1-pentanol.

So therefore, we can confirm that the compound from above the correct order of boiling point from the highest to the lowest is 1-pentanol, 1-bromopentane, pentane and propane respectively.

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As per the standard data, the heat evolved during one mole of calcium carbonate decomposes is 177.8 KJ. Thus 15 g or 0.15 moles of calcium carbonate when decomposed will produce 26.67 KJ of heat.

Reaction enthalpy of a substance is the heat evolved or absorbed during a reaction. Reaction enthalpy is negative for an exothermic reaction and positive for an endothermic reaction.

Molar mass of calcium carbonate = 100 g.

no.of moles in 15 g = 15 /100 = 0.15 moles.

One mole or 100 g of calcium carbonate decompose to evolve 177.8 KJ according to the scientific record.

Thus, heat evolved by the decomposition of 0.15 moles is 0.15 × 177.8 KJ = 26.67 KJ.

Hence, the heat evolved during the decomposition of 15 g of calcium carbonate is 26.67 KJ.

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The question requires us to balance a given reaction and then determine the excess reagent for this same reaction, given that 3.4 moles of Ca(NO3)2 and 2.4 moles of LiPO4 are used.

First, let's balance the equation so we can make the required calculations from it. A simple way to balance this reaction is to start with metals (Li and Ca) and consider the anions NO3 and PO4 instead of the isolated N, O and P atoms:

1) We write the given equation:

___Ca(NO3)2 + ____Li3PO4 --> ___LiNO3 + ____Ca3(PO4)2

2) We check the amount of Ca and Li on both sides of the reaction:

On the left side -> 1 Ca and 3 Li

On the right side -> 3 Ca and 1 Li

3) Then, we change the coefficients in order to have the same amount of Ca and Li on both sides:

3

4) Next, we check the amount of NO3 and PO4 anions:

Left side -> 3*2 NO3 = 6 NO3 and 1 PO4

Right side -> 3*1 NO3 = 3 and 2 PO4

4) We need to adjust some numbers in order to have the same amount of all considered species:

5) At last, we check again:

Left side -> 3 Ca, 6 NO3, 6 Li, 2 PO4

Right side -> 3 Ca, 6 NO3, 6 Li and 2 PO4

a) Then, the balanced reaction is:

1

b) Now that we know the stoichiometric coefficients, we can determine the excess reagent.

From the balanced reaction, we know that we need 3 moles of Ca(NO3)2 to react with 2 moles of Li3PO4. Then, we can write:

3 mol Ca(NO3)2 --------------- 2 mol Li3PO4

3.4 mol Ca(NO3)2 ------------ x

exexcesslimiting (more than 2.27 moles)

We can also determine the excess reactant from the following relation:

y ------------- 2.4 mol Li3PO4

In this case, solving for y, we have that we would need 3.6 moles of Ca(NO3)2 to react with 2.4 moles of Li3PO4, meaning that there is less than required of Ca(NO3)2, thus this is the limiting reactant while Li3PO4 is the excess reactant.

Although sodium and phosphorus are both found in the same period of the periodic table, the nature of their oxides is different. Although P2O5 is acidic, Na2O is basic.

Metal oxides are basic, whereas non-metal oxides are acidic. The metallic character of the elements lessens as you move from left to right over time, while the non-metallic character grows.

Since the oxides in an element's higher oxidation state are more acidic than those in its lower oxidation state, dinitrogen pentoxide is the most acidic oxide compared to nitrogen dioxide and nitrogen tetraoxide.

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After 1.5 days, only 1.25 mg of technetium-99m will remain out of the original 80 mg that was prepared.

Technetium-99m (99mTc) is a radioactive isotope that is used in medical imaging.

It has a half-life of 6 hours, which means that after 6 hours, half of the original amount of technetium-99m will have decayed.

Therefore, after another 6 hours (12 hours total), half of the remaining technetium-99m will have decayed, leaving only 25% of the original amount.

After another 6 hours (18 hours total), half of the remaining technetium-99m will have decayed again, leaving only 12.5% of the original amount.

After 1.5 days, which is 36 hours total, we can use the formula for radioactive decay to calculate how much technetium-99m will remain: amount remaining = original amount x \((1/2)^{t/h}\) where t is the time elapsed and h is the half-life.

Plugging in the given values, we get: amount remaining = 80 mg x (1/2)^(36/6) amount remaining = 80 mg x \((1/2)^{6}\) amount remaining = 80 mg x 0.015625 amount remaining = 1.25 mg

Therefore, after 1.5 days, only 1.25 mg of technetium-99m will remain out of the original 80 mg that was prepared.

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Answer:

71%

Explanation:

Total weight = 700g

Active weight = 500g

% of active ingredient = \(\frac{active weight}{total weight} *100\)

\(\frac{500}{700}* 100\) = 0.71 * 100 = 71%

The balanced equation of the redox reaction is given as follows:

The balanced equation of the reaction is determined using the half-reaction method.

The given equation of the redox reaction is:

H₆TeO₆ + Br₂ ----> TeO₂ + BrO₃⁻

Reduction half-reaction:

H₆TeO₆ → TeO₂

The oxidation state of Te changes from +6 to +4, showing that it has lost gained electrons.

H₆TeO₆ → TeO₂ + 2e⁻

Oxidation half-reaction:

Br₂ → BrO₃⁻

The oxidation state of Br changes from 0 to +5, showing that it has lost five electrons.

Balancing the electrons transferred and the atoms by adding electrons, H₂O, and H⁺ to the appropriate sides:

Br₂ + 6 H₂O → 2 BrO₃⁻ + 12 H⁺ + 10 e⁻

The number of electrons transferred in both half-reactions balanced is  by multiplying the oxidation half-reaction by 5 and the reduction half-reaction by 2:

5 (H₆TeO₆ → TeO₂ + 2 e⁻) → 5 H₆TeO₆ → 5 TeO₂ + 10 e⁻

2 * (Br₂ + 6H₂O → 2 BrO₃⁻ + 12 H⁺ + 10e⁻) → 2 Br₂ + 12 H₂O → 4 BrO₃⁻ + 24 H⁺ + 20 e⁻

The two half-reactions are added together and the electrons are canceled out to obtain the balanced redox reaction:

5 H₆TeO₆ + 2 Br₂ + 12 H₂O → 5 TeO₂ + 4 BrO₃⁻ + 24 H⁺

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If the diameter of an atom is 1 × 10⁻⁸ cm, the diameter of the nucleus is approximately 1 × 10⁻¹² cm, since the atom is mostly empty space.

The nucleus is the part of an atom that contains more than 99.9% of its mass, represented by protons and neutrons.

The diameter of an atom is 1 × 10⁻⁸ cm. The nucleus is about 10,000 times smaller than the atom. Thus, the diameter of the nucleus is:

d(nucleus) = d(atom) / 10,000

d(nucleus) = 1 × 10⁻⁸ cm / 10,000 = 1 × 10⁻¹² cm

If the diameter of an atom is 1 × 10⁻⁸ cm, the diameter of the nucleus is approximately 1 × 10⁻¹² cm, since the atom is mostly empty space.

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Answer:C

Explanation:

C. Boiling point

Stacy is most likely testing the boiling point of the liquid in each vial. By heating the vials on the hot plate, he is increasing the temperature of the liquid and observing when it begins to boil. Boiling point is a physical property of a substance that is affected by factors such as pressure and temperature. It is the temperature at which the vapor pressure of the liquid is equal to the pressure exerted on the liquid by its surroundings. Therefore, by testing the boiling point of the liquid, Stacy can determine its identity or purity.

An electron from of the M shell occupying a hole in the K shell at 69 keV expelled as you move from the outside in to the inside will be moving to an energy levels with an ionization energy of 70 keV  -2 keV,

The minimal energy needed to ionize an atom is sufficient to eject an electron from its ground state. Ionization energy has a periodic trend that rises across the chemical elements form top to bottom as well as from left to right.

As you move from left to right along a period just on periodic table, the initial ionization energy often rises. This is because when nuclear charge rises, the outermost electron becomes more tightly connected to the nucleus.

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Answer:

No. Moles  = 2.142   mole

The pH of a 0.250 M solution of HOC6H5 is 2.92 and HCN is 5.96

a. HOC6H5, or benzoic acid, is a weak acid that partially dissociates in water to form H+ and C6H5COO- ions. The dissociation reaction is

HOC6H5 ⇌ H+ + C6H5COO-

To determine the pH of a 0.250 M solution of benzoic acid, we need to calculate the concentration of H+ ions in solution. The equilibrium expression for the dissociation reaction is:

Ka = [H+][C6H5COO-]/[HOC6H5]

where Ka is the acid dissociation constant for benzoic acid. The value of Ka for benzoic acid is 6.5 × \(10^-5.\)

We can assume that the initial concentration of H+ ions in the solution is zero. At equilibrium, let x be the concentration of H+ ions in solution and 0.250 - x be the concentration of C6H5COO- ions in solution. Then:

Ka = x(0.250 - x)/0.250

Solving for x, we get:

x = 1.21 × \(10^-3\) M

the pH of a 0.250 M solution of benzoic acid is:

pH = -log[H+] = -log\((1.21 × 10^-3)\) = 2.92

b. HCN, or hydrocyanic acid, is also a weak acid that partially dissociates in water to form H+ and CN- ions. The dissociation reaction is:

HCN ⇌ H+ + CN-

To determine the pH of a 0.250 M solution of HCN, we need to calculate the concentration of H+ ions in solution. The equilibrium expression for the dissociation reaction is:

Ka = [H+][CN-]/[HCN]

where Ka is the acid dissociation constant for HCN. The value of Ka for HCN is 4.9 ×\(10^-10\).

We can assume that the initial concentration of H+ ions in the solution is zero. At equilibrium, let x be the concentration of H+ ions in solution and 0.250 - x be the concentration of CN- ions in solution. Then:

Ka = x(0.250 - x)/0.25

Solving for x, we get:

x = 1.1 × \(10^-6\) M

pH :- -log[H+] = -log\((1.1 × 10^-6)\)

= 5.96

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Answer:

48 hours

Explanation:

Because if the world would spin regularly, then it would take 24 hours. But if it spins half as fast, then it would be 2x more.

The correct equation that has been balanced is option (c): ZnS + 02 -> 2ZnO + SO2. This equation is balanced because the number of sulfur atoms (1 on each side) and the number of oxygen atoms (2 on each side) are equal.

The correct equation that has been balanced is option (c): ZnS + 02 -> 2ZnO + SO2. To determine whether an equation is balanced, we need to ensure that the number of atoms of each element is the same on both sides of the equation. Let's analyze each option:

(a) 2ZnS + 302 -> 2ZnO + 2SO2: This equation is unbalanced because there are an unbalanced number of oxygen atoms (7 on the left side and 4 on the right side) compared to the amount of sulphur atoms (2 on each side).

(b) ZnS + 02 --> ZnO + SO2: This equation is unbalanced because there are an unbalanced number of oxygen atoms (2 on the left side and 3 on the right side) compared to the sulphur atoms (1 on each side).

(c) ZnS + 02 -> 2ZnO + SO2: This equation is balanced because the number of sulfur atoms (1 on each side) and the number of oxygen atoms (2 on each side) are equal. Therefore, option (c) is the only equation that has been balanced correctly.

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Answer:
0.1518 moles of CaCO3 can be produced.

Explanation:

The balanced chemical equation for the reaction between calcium bicarbonate and calcium hydroxide is:

Ca(HCO3)2 + Ca(OH)2 → 2CaCO3 + 2H2O

From this equation, we can see that 1 mole of Ca(HCO3)2 produces 2 moles of CaCO3.

The molar mass of Ca(HCO3)2 is:

1 Ca atom = 40.08 g/mol

2 H atoms = 2.02 g/mol

2 CO3 molecules = 2 x 60.01 g/mol = 120.02 g/mol

So, the molar mass of Ca(HCO3)2 is:

40.08 + 2.02 + 120.02 = 162.12 g/mol

To find the number of moles of Ca(HCO3)2 in 12.3 g, we use the formula:

moles = mass / molar mass

moles = 12.3 g / 162.12 g/mol

moles = 0.0759 mol

According to the balanced equation, 1 mole of Ca(HCO3)2 produces 2 moles of CaCO3. Therefore, 0.0759 moles of Ca(HCO3)2 will produce:

moles of CaCO3 = 2 x moles of Ca(HCO3)2

moles of CaCO3 = 2 x 0.0759

moles of CaCO3 = 0.1518 mol

Therefore, 0.1518 moles of CaCO3 can be produced.

1. The IUPAC name of N is nitrogen.

2. Nitrogen dioxide

3.The IUPAC name of O is oxygen

4.The IUPAC name of OH is hydroxyl.

The IUPAC name of ·0 is a radical. It is commonly found in organic chemistry and plays an important role in many reactions.

IUPAC names for the given compounds are:1.1. N: Nitrogen

The IUPAC name of N is nitrogen.

It is a non-metal and belongs to group 15 in the periodic table. It has an electronic configuration of 1s2 2s2 2p3.1.2. NO2: Nitrogen dioxide

Explanation: NO2 is a chemical compound that is formed by the combination of nitrogen and oxygen. It is a reddish-brown gas that has a pungent odor.

The IUPAC name of NO2 is nitrogen dioxide.1.3. O: Oxygen

Explanation: The IUPAC name of O is oxygen.

It is a non-metal and belongs to group 16 in the periodic table. It has an electronic configuration of 1s2 2s2 2p4.

X: UnknownExplanation: No IUPAC name can be given to an unknown compound as the structure and composition are not known.

Y: Hydroxyl Explanation: The IUPAC name of OH is hydroxyl.

It is a functional group that is composed of an oxygen atom and a hydrogen atom (-OH). It is commonly found in alcohols and phenols. ·0: RadicalExplanation: A radical is a molecule or an ion that contains an unpaired electron.

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Note: The complete question is given below

Provide the IUPAC names for the following compounds:

\(CH_3CH_2CH(CH_3)CH_2CH_2CH_2CH_3\)

C6H5CH(CH3)2

H2NCH2CH2CH2CH2CH2NH2

CH3CH2CH2CH2CH2OH

CH3CH2CH2CHOHCH3

Motor proteins such as myosin are able to generate force by undergoing a series of conformational changes.

Conformational change in protein is an important aspect for the protein functioning. Proteins need to be switched off and on based on the requirements. For this, ligands usually activate or deactivate the proteins.

Protofilaments are the structures that are associated with cytoskeleton structures of the cells. Adding amino acids is done while translation but not after that. However, cleavage may occur depending the ongoing process.

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Answer:

The air warms up, causing it to become lighter than the cold air outside of it.

The volume in millilitres of 2.37M potassium hydroxide that contains 9.29g of solute is 70mL.

Volume of a solution can be calculated from the molarity, which is the concentration of a substance in solution, expressed as the number moles of solute per litre of solution.

Molarity = no of moles ÷ volume

no of moles = mass ÷ molar mass

Molar mass of pottasium hydroxide (KOH) = 56.1056 g/mol

moles = 9.29g ÷ 56.1056 g/mol = 0.166moles

2.37 = 0.166/V

V = 0.166 ÷ 2.37

V = 0.07L

Volume in millilitres = 70mL

Therefore, 70mL is the volume of the pottasium hydroxide solution.

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The height of the octagonal prism of volume 30 ft³ is 3.75 ft.

Height is the vertical distance between two points.

To calculate the height of the octagonal prism, we use the formula of volume below.

Formula:

Where:

From the question,

Given:

Substitute these values into equation 1 and solve for h

Hence, the height of the octagonal prism is 3.75 ft.

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answer: c- new knowledge showed that the exact location of electrons can not be known.

Explanation: i just did it ;)

Answer:

the relationship between the relative quantities of substances taking part in a reaction or forming a compound, typically a ratio of whole integers.

Explanation:

G o o g l e

Explanation:

Stoichiometry is the calculation of reactants and products in chemical reactions in chemistry.