Sasha pulls a block across the floor at a constant speed. Why doesn't the motion of the block change even though Sasha is pulling on it?

7. the pH of 0.81 M Mg(OH)₂ solution is 9.19.

8. the pH of 0.27 M pyridine solution is 9.11.

Mg(OH)₂ is a base which dissociates to produce two OH⁻ ions.

Mg(OH)₂ → Mg²⁺ + 2 OH⁻

Let the concentration of OH⁻ ions produced be x.

Therefore, the concentration of Mg²⁺ is 0.81-x

Mg(OH)₂ → Mg²⁺ + 2 OH⁻

Initial concentration (M)    0         0

Change (M)                 -x         +2x

Equilibrium Concentration  0.81-x      x     x

Using Kb for Mg(OH)₂,Kb = Kw/Ka

Kw = 1.0 × 10⁻¹⁴ at 25 °C.

For Mg(OH)₂,Kb = [Mg²⁺][OH⁻]²/Kw= (x)²/0.81 - x

Kb = 4.5 × 10⁻¹² = x²/0.81 - x

On solving the equation,x = 7.7 × 10⁻⁶M

Therefore, the concentration of OH⁻ ions = 2 × 7.7 × 10⁻⁶ = 1.54 × 10⁻⁵ M

To calculate the pH of the solution, use the formula:

pOH = - log [OH⁻]= - log 1.54 × 10⁻⁵pOH = 4.81pH = 14 - 4.81 = 9.19

Thus, the pH of 0.81 M Mg(OH)₂ solution is 9.19.

Let the concentration of OH⁻ ions produced be x.

Therefore, the concentration of C₅H₅NH⁺ is 0.27 - x.

C₅H₅N + H₂O ⇌ C₅H₅NH⁺ + OH⁻

Initial concentration (M)   0.27      0

Change (M)                -x       +x

Equilibrium Concentration  0.27-x     x

Using Kb for C₅H₅N,Kb = Kw/Ka

Kw = 1.0 × 10⁻¹⁴ at 25 °C.

For C₅H₅N,

Kb = [C₅H₅NH⁺][OH⁻]/[C₅H₅N]= (x) (x)/(0.27-x)Kb = 1.7 × 10⁻⁹

= x²/(0.27-x)

On solving the equation,

x = 1.3 × 10⁻⁵ M

Therefore, the concentration of OH⁻ ions = 1.3 × 10⁻⁵ M

To calculate the pH of the solution, use the formula:

pOH = - log [OH⁻]= - log 1.3 × 10⁻⁵pOH

= 4.89pH = 14 - 4.89 = 9.11

Thus, the pH of 0.27 M pyridine solution is 9.11.

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Answer:

1.14 moles of oxygen will react

Explanation:

The balanced equation of reaction between iron and oxygen is  

4 Fe + 3 O₂  → 2 Fe₂O₃

By stoichiometry of the reaction (that is, the relationship between the amount of reagents and products in a chemical reaction), the following amounts of each compound participate in the reaction:

The molar mass of iron being Fe 55.85 g/mole, then the following amount of mass reacts by stoichiometry: 4 moles* 55.85 g/mole=223.4 g

You can apply the following rule of three: if by stoichiometry 223.4 grams of Fe react with 3 moles of O₂, 84.9 grams of Fe react with how many moles of O₂?

\(moles of O_{2} =\frac{84.9 grams of Fe*3 moles ofO_{2} }{223.4 grams of Fe}\)

moles of O₂= 1.14 moles

1.14 moles of oxygen will react

Answer:

To identify a pure liquid substance using the physical properties of solubility, density, and boiling point. The physical properties of a pure substance can be measured without changing the composition of the substance.

Explanation:

The oxidation state of an individual carbon atom in CaCO3 is +4. The oxidation state of an individual carbon atom in compounds is often determined by analyzing the compound's structure. In the case of CaCO3, the compound is composed of a carbon atom, two oxygen atoms, and a calcium atom. The oxygen atoms are electronegative and will pull electrons away from the carbon atom. As a result, the carbon atom will be oxidized.

In this compound, there are three oxygen atoms (-2 each) and one calcium atom (+2). To calculate the oxidation state of the carbon atom, we can use the following formula:

Oxidation state of C + 3 × oxidation state of O + oxidation state of Ca = 0

Let's plug in the values we know:

Oxidation state of C + 3 × (-2) + (+2) = 0

Simplifying this equation gives us:

Oxidation state of C = +4

Therefore, the oxidation state of the individual carbon atom in CaCO3 is +4.

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Answer:

Explanation:

NaOH + KNO3 --> NaNO3 + KOH. combustion. CH4 + 2 O2 --> CO2 + 2 H2O. single displacement. 2 Fe + 6 NaBr --> 2 FeBr3 + 6 Na. double displacement.

Answer:

D in addition to the original sample. In a file cabinet, she finds a paper labeled "Electrochemistry Activity" which lists five metals: zinc, aluminum, magnesium, silver and tin She is not able to find anything that identifies which metals correspond to which letters. She makes some quick observations, summarized below.

Explanation:

2H₂ + O₂ ⇒ 2H₂ for this reaction the volume of water vapor produced when 8 grams of H₂ reacts at STP is 179.2 Litre.

The standard temperature and pressure (STP) adverts to the nominal conditions in the atmosphere at sea level. These conditions are 0 degrees Celsius and 1 atmosphere (atm) of pressure.

The formula for STP can be represented as, VP = nRT.

"P" is pressure, "V" is volume, n is the number of moles of a gas, "R" is the molar gas constant and "T" is temperature.

Given:

Number of mole = 8 grams

8 g of hydrogen = 8 × 1

= 8 mol.

At STP 1 mole H₂ occupies 22.4 L volume.

Therefore, 8 moles of hydrogen occupy = 8 × 22.4

= 179.2 L.

Thus, the volume of water vapor produced when 8 grams of H₂ reacts at STP is 179.2 Litre.

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Answer:

1/4 of the offspeing will have the red flowers

Answer:

B (0.39 mol).

Explanation:

Hope this helped!

Answer:

True

Explanation:

Answer:

False

Explanation:

To make 1 liter of a 10% NaCl solution from a solid stock, you will require the following materials and containers.MaterialsSolid NaClDistilled water1-Liter volumetric flask250-mL volumetric flask 2-beakersProcedureTo prepare 1 liter of a 10% NaCl solution, the following procedure should be followed:Measure out 100g of NaCl using a balance.

Measure the weight of an empty 250-mL volumetric flask.Add the NaCl to a 250-mL beaker and add a small amount of distilled water to it to dissolve the NaCl.Carefully pour the dissolved NaCl solution into the 250-mL volumetric flask. Add distilled water to the mark on the flask to make up the volume. Stopper the flask and invert it several times to mix the solution.Measure the weight of the 1-Liter volumetric flask.Add the 250-mL volumetric flask solution to a 1-Liter volumetric flask.Add distilled water to the mark on the flask to make up the volume.

Stopper the flask and invert it several times to mix the solution.The final volume of the solution will be 1 liter of a 10% NaCl solution.PrecautionsEnsure the NaCl has completely dissolved before adding more water to avoid making a less concentrated solution.Measure the weight of the volumetric flask before and after adding the solution to calculate the volume of solution that was added.Use distilled water to prepare the solution.

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Answer:

C. pH > pOH; Kw = 1.0 * 10^-14

Explanation:

The ion product of water, Kw = [H+]*[OH-] = 1.0 * 10^-14. It is a constant.

When an acid or base is added to water, its ion product does not change as it a constant. However, the relative concentrations of H+ ions and OH- ions will change depending on whether an acid or base is added to water.

When an acid is added to water, the concentration of H+ ions increases while that of OH- ions decreases, and vice versa.

Therefore, in the above situation where an acid is added to water, pH > pOH; Kw = 1.0 * 10^-14

In this question, we have:

31.1 grams of O2

84.3 grams of F2

94.9 L of total volume

55.77°C of temperature which is equal to 328.92 K

Now, to find the pressure of this container, we can find the number of moles of each gas, and add both values together making it one value of moles and then we will use the Ideal gas law to find the pressure, so let's start with O2

The molar mass of O2 is 32g/mol and we have 31.1 grams

32g = 1 mol

31.1g = x moles

x = 0.972 moles of O2

Now for F2, the molar mass is 38g/mol, and we have 84.3 grams

38g = 1 mol

84.3g = x moles

x = 2.22 moles of F2

Now we add these values, 0.972 + 2.22 = 3.192 moles

And now we can use the ideal gas law formula:

PV = nRT

Remember that R is the gas constant, 0.082

P * 94.9 L = 3.192 * 0.082 * 328.92

94.9P = 86.1

P = 0.91 atm

Using the specified mass and each compound's respective molecular weights, we can compare the number of moles of each compound:

CH4O: Methyl alcohol has a molecular weight of about 32 g/mol.The formula for calculating the number of moles of CH4O is (mass of CH4O) / (molecular weight of CH4O): 2.0 g / 32 g/mol = 0.0625 moles.
H2O: H2O (water) has a molecular weight of about 18 g/mol.H2O's mass divided by its molecular weight yields the number of moles: 2.0 g divided by 18 g/mol, or 0.111 moles.
CHO: CHO (formaldehyde) has a molecular weight of about 30 g/mol.The formula for calculating the number of moles of CHO is (mass of CHO) / (molecular weight of CHO): 2.0 g / 30 g/mol = 0.067 moles.Consequently, the chemicals are CH4O CHO H2O in ascending molecular weight order.


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The molarity of the solution is 0.833 M NaOH.

To calculate the molarity (M) of a solution, you need to determine the number of moles of solute (in this case, NaOH) and divide it by the volume of the solution in liters.

First, convert the given mass of NaOH to moles using its molar mass. The molar mass of NaOH is 22.99 g/mol for Na, 16.00 g/mol for O, and 1.01 g/mol for H. So, the molar mass of NaOH is 22.99 + 16.00 + 1.01 = 40.00 g/mol.

Number of moles of NaOH = 20.0 g / 40.00 g/mol = 0.500 mol.

Next, divide the number of moles by the volume of the solution in liters:
Molarity (M) = 0.500 mol / 2.40 L = 0.208 M.

Therefore, the molarity of the solution prepared is 0.208 M NaOH.

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The form of chemical weathering that is responsible for breaking the serpentinite down on Ruby Jones Hall is hydrolysis.

Hydrolysis is a type of chemical weathering that occurs when minerals in rocks react with water and create new compounds as a result. It is particularly important in the weathering of silicate minerals, including the serpentinite found on Ruby Jones Hall. During hydrolysis, water molecules split into hydrogen and hydroxide ions and then react with the minerals. This reaction alters the minerals and creates new ones, often resulting in a softer, weaker rock that is more easily eroded. The process of hydrolysis breaks down the serpentinite on Ruby Jones Hall. Serpentinite is a rock made primarily of the mineral serpentine.

Serpentine is a magnesium-rich mineral that is susceptible to hydrolysis because it reacts readily with water to form other minerals. When water reacts with serpentine, it breaks down the mineral and produces new minerals, including clay minerals like kaolinite and smectite. These new minerals are much softer and more easily eroded than the original serpentine, which is why serpentinite is often found in areas with high rates of weathering and erosion.

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The reaction of \(2.50 L B$_2$H$_6$\) and \(5.65 L Cl$2$\) at STP produces \($-145.2\ kJ$\) of energy, based on the balanced equation with \(\Delta H{rxn} = -1396\ kJ$.\)

To calculate the energy that evolved during the reaction of 2.50 L \(B$_2$H$_6$ and 5.65 L Cl$_2$\), we need to first determine the number of moles of each gas.

Using the ideal gas law, we can calculate the number of moles of \(B$_2$H$_6$ and Cl$_2$\)at STP (Standard Temperature and Pressure):

\($PV = nRT$\)

\(V =$ 2.50 L B$_2$H$_6$\) at STP

\(T =$ 273 K\)

\(R =$ 0.0821 L atm/(mol K)\)

\(P =$ 1 atm at STP\)

\($n_{B_2H_6} = \frac{PV}{RT} = \frac{(1 atm)(2.50 L)}{(0.0821 L\ atm\ mol^{-1}\ K^{-1})(273 K)} = 0.104\ mol\ B_2H_6$\)

Similarly, for\(Cl$_2$\), we have:

\(V =$ 5.65 L Cl$_2$\) at STP

\($n_{Cl_2} = \frac{PV}{RT} = \frac{(1 atm)(5.65 L)}{(0.0821 L\ atm\ mol^{-1}\ K^{-1})(273 K)} = 0.252\ mol\ Cl_2$\)

Since the reaction equation shows that 6 moles of \(Cl$_2$\) react with 1 mole of \(B$_2$H$_6$\), we have an excess of \(Cl$_2$\) in this case, and we can assume that all the \(B$_2$H$_6$\) is consumed during the reaction.

Therefore, the amount of energy evolved during the reaction of 0.104 mol\(B$_2$H$_6$\) and 0.252 mol \(Cl$_2$\) is given by:

\($\Delta H_{rxn} = -1396\ kJ/mol$\)

Multiplying this by the number of moles of \(B$_2$H$_6$\) gives:

\($\Delta H = \Delta H_{rxn} \times n_{B_2H_6} = -1396\ kJ/mol \times 0.104\ mol = \boxed{-145.2\ kJ}$\) of energy evolved during the reaction.

The negative sign indicates that the reaction is exothermic, meaning that it releases energy.

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Answer: b

Explanation:

The two variables that the students definitely controlled during the investigation are:

The volume of acid used: The students used equal volumes of acid in each test. Controlling the volume of acid ensures that the amount of acid is the same in each test, which helps to keep this variable constant.

The length of magnesium ribbon used: The students used equal lengths of magnesium ribbon in each test. Controlling the length of magnesium ribbon ensures that the amount of magnesium is the same in each test, which helps to keep this variable constant.

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Since it dissociates almost entirely, HCl is a powerful acid.

In contrary, a weak acid like acetic acid (CH3COOH) does not dissociate well in water because it retains a large number of bound-up H+ ions.

Acetic acid splits into CH3COO, and H+.

In conclusion, the amount of free H+ ions discharged into solution increases with acid strength. The pH value for that acid is inversely correlated with the amount of free H+.

Because they allow other molecules to bind to H+ ions in solution, acids are frequently referred to as H+ ion donors.

Any acid that is entirely ionized in an aqueous solution is considered to be strong. When present in water, hydrogen chloride (HCl) totally ionizes to produce hydrogen and chloride ions.

Weak acid is one that ionizes very little in an aqueous solution. A very well-liked weak acid that is present in vinegar is acetic acid.

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In a TLC experiment, the compound with the larger Rf value will elute faster. In the case of naphthalene and 1-bromonaphthalene, the 1-bromonaphthalene will elute faster and have a larger Rf value.

This is because 1-bromonaphthalene is more polar than naphthalene. Polar compounds have a stronger attraction to the polar stationary phase (such as the silica gel in TLC plates) and will interact more with it, resulting in a lower Rf value.

Naphthalene, on the other hand, is less polar and will have a weaker interaction with the stationary phase, allowing it to travel further and have a higher Rf value.

The polarity of a compound is determined by the presence of functional groups or atoms that create an uneven distribution of charge or electronegativity. In this case, the bromine atom in 1-bromonaphthalene increases its polarity compared to naphthalene, leading to a stronger interaction with the stationary phase.

In summary, the 1-bromonaphthalene will elute faster in a TLC experiment and have a larger Rf value compared to naphthalene due to its higher polarity resulting from the presence of a bromine atom.

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In recent years, the output of ammonia has remained mostly steady. Ammonia output was projected to reach 150 million metric tonnes worldwide in 2022. With over 64.6 million metric tonnes produced, East Asia has the largest ammonia output.

Sodium metal is produced via the Castner method, which involves electrolyzing molten sodium hydroxide at a temperature of around 330 °C. At that temperature, the molten sodium would begin to dissolve in the melt; below that temperature, the liquid would harden.

One mole (or one gramme) of sodium chloride (NaCl) has a molecular weight of 58.44, making 58.44g the molecular weight of one gramme. You may create 1M NaCl by dissolving 58.44g of sodium chloride in a final amount of 1 litre.

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Glycine is the N-terminal residue and Serine is the C-terminal residue.

From the given polypeptide Gly-Tyr-Gly-Phe-Met-Ser, the correct statements are:

Glycine is the N-terminal residue: This is correct because glycine is the first amino acid in the sequence, making it the N-terminal residue.

Serine is the C-terminal residue: This is correct because serine is the last amino acid in the sequence, making it the C-terminal residue.

Methionine is the N-terminal residue: This statement is incorrect. Although methionine is present in the sequence,

it is not the first amino acid. Glycine is the first amino acid, so it is the N-terminal residue.

Therefore, the correct statements are:

Glycine is the N-terminal residue.

Serine is the C-terminal residue.

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Answer:

39.2

Explanation:

1.75 moles × 22.4 liters = 39.2

The predicted intermediate that can directly supply the carbon skeleton for the synthesis of a five-carbon amino acid, is a-ketoglutarate. Correct answer: letter D.

This is because a-ketoglutarate is an intermediate of the Krebs cycle, and as such can directly supply the carbon skeleton for the synthesis of a five-carbon amino acid.

Five-carbon amino acids are essential for the synthesis of proteins in the body. a-Ketoglutarate is a key intermediate in the Krebs cycle that can directly supply the carbon skeleton for the synthesis of a five-carbon amino acid.

This makes a-ketoglutarate an important molecule for the synthesis of proteins in the body.

Which intermediate would you predict may directly supply the carbon skeleton for synthesis of a five-carbon amino acid?

Group of answer choices:

A) succinate

B) malate

C) cotrate

D) a-ketoglutarate

E) isocitrate

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According to the Brønsted-Lowry model, an acid and its conjugate base differ by a single proton, while a base and its conjugate acid differ by the addition of a single proton. If a reaction produces conjugate acid-base pairs, it supports this model.

To determine if the reaction supports the Brønsted-Lowry model of acids and bases, there are several questions that could be asked. Two possible questions are:

1. Does the reaction involve the transfer of protons (H+ ions) from one molecule to another.This is a key concept in the Brønsted-Lowry model, which defines acids as proton donors and bases as proton acceptors. If a reaction involves the transfer of protons, it supports this model.

2. Do the reactants and products contain conjugate acid-base pairs.

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Answer:

1. Did an acid donate a hydrogen ion to become a conjugate base?

2. Did a base accept a hydrogen ion to become a conjugate acid?

The mole fraction of carbon dioxide in the mixture is

P(CO₂) = 0.00004 × 76mmHg

           = 0.304mmHg

The key to this problem is the fact that each component of a gas mixture contributes to the total pressure exerted by the mixture in proportion to the number of molecules in the mixture.

Partial pressures of gases are most often expressed as mole fractions.

                    P(gas) = χ(gas) × P(mixture)

This is the proportional to the number of molecules.

As you know, 1 mole of a substance is exactly 6.022⋅10²³

molecules of that substance. This is known as the Avogadro number Nₐ.

This means that the number of molecules, say x and Avogadro's number

No. can be used to express the number of moles of a gas.

             From a mole =  Number of Molecules × Nₐ

Now, the percentage composition of a gas mixture is the number of molecules each gas contributes to 100 molecules of the mixture.

In this case, the air must contain 0.04% carbon dioxide. This means that there are 0.04 CO₂ molecules in 100 air molecules.

For example, the number of moles of carbon dioxide in 100 air molecules is ⁿCO² = 0.04 molecules × Nₐ

            = 0.04 Nₐ

This air sample is

n (total) = 100 molecules × Nₐ

            = 100⋅Nₐ

This means that the mole fraction of carbon dioxide in the mixture is

P(CO₂) = 0.00004 × 76mmHg

           = 0.304mmHg

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