at the end of 14 min, 1/16 of a sample of radioactive polonium remains. the corresponding half-life is

The freezing point of the solution of 645 g of urea, H₂NCONH₂, dissolved in 980 g of water is -20.39 °C

First, we shall determine the mole in 645 g of urea, H₂NCONH₂. Details below:

Mole = mass / molar mass

Mole of H₂NCONH₂ = 645 g / 60.06

Mole of H₂NCONH₂ = 10.74 moles

Next, we shall obtain the molality of the solution. Details below:

Molality = mole / mass of solvent (in kg)

Molality = 10.74 / 0.98

Molality = 10.96 m

Next, we shall determine the freezing point depression. This is shown below

ΔTf = Kf × molality

ΔTf = 1.86 × 10.96  

ΔTf = 20.39 °C

Finally, we shall obtain the freezing point of the solution. This is show below:

Freezing point of solution = 0 - ΔTf

Freezing point of solution = 0 - 20.39

Freezing point of solution = -20.39 °C

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Among the options, the compounds likely to form are:

The formation of these compounds is possible because strontium (Sr) is a metal with a positive charge, and chlorine (Cl) and iodine (I) are nonmetals with negative charges. Strontium can lose two electrons to form Sr²⁺, and it can also lose three electrons to form Sr³⁺.

Chlorine can gain one electron to form Cl⁻, and iodine can gain one electron to form I⁻. Therefore, strontium can combine with chlorine to form SrCl₂ and with iodine to form SrI₃.

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The structural isomer of 2-methylbutane is butane (c). The structural isomers are the compounds that have the same molecular formula but different arrangements of atoms.

The molecular formula of 2-methylbutane is C5H12.

(a) Propane has the molecular formula C3H8 and is not a structural isomer of 2-methylbutane.

(b) 2-methylpropane also known as isobutane has the molecular formula C4H10 and is not a structural isomer of 2-methylbutane.

(c) Butane has the molecular formula C4H10 and is a structural isomer of 2-methylbutane. The structural formula of butane is CH3CH2CH2CH3, while the structural formula of 2-methylbutane is CH3CH(CH3)CH2CH3.

(d) Pentane has the molecular formula C5H12 but it is not a structural isomer of 2-methylbutane because it has a longer carbon chain.

Therefore, the structural isomer of 2-methylbutane is butane (c).

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The angular momentum quantum number (l) in a hydrogen atom determines several properties of the orbitals. Firstly, it determines the shape of the orbital.

Orbitals with different angular momentum quantum numbers have different shapes, such as s, p, d, and f orbitals. Secondly, it determines the possible orientation of the orbital in space. Orbitals with higher angular momentum quantum numbers have more complex orientations. Thirdly, it determines the energy of the orbital. Orbitals with higher angular momentum quantum numbers have higher energies, which affects the overall energy level of the atom. Finally, it also indirectly determines the possible number of electrons that can occupy a particular orbital, as the Pauli exclusion principle and the Aufbau principle dictate that each orbital can only hold a maximum of two electrons with opposite spins. Therefore, the angular momentum quantum number plays a crucial role in determining the properties and behavior of electrons in hydrogen atoms.

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The bicarbonate buffer system is a commonly used buffer in biochemical experiments, especially in studying enzymes and proteins.

The procedure used for the preparation of bicarbonate buffer involves the addition of sodium bicarbonate to a solution of carbon dioxide in water, which results in the formation of carbonic acid. This acid can then dissociate into bicarbonate ions and hydrogen ions, forming a buffer system. While this procedure is a valid one for buffer preparation, there are some limitations. The buffer capacity of the bicarbonate buffer system is relatively low compared to other buffer systems, and it is also sensitive to changes in temperature and pH. Therefore, the use of bicarbonate buffer should be carefully considered and optimized for specific experimental conditions.

Yes, the procedure used for the bicarbonate buffer is a valid one for buffer preparation. Bicarbonate buffer systems are widely used due to their capacity to maintain pH stability. They are commonly prepared using a combination of sodium bicarbonate (NaHCO3) and sodium carbonate (Na2CO3) or a weak acid like carbonic acid (H2CO3). By adjusting the ratio of these components, the desired pH can be achieved. The bicarbonate buffer is particularly important in physiological systems, as it plays a crucial role in maintaining blood pH within the narrow range required for optimal biological function. Its effectiveness as a buffer is attributed to the equilibrium between dissolved CO2, H2CO3, and bicarbonate ions.

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146 g sodium chloride is formed when 1.25 moles of chlorine gas react vigorously with excess sodium.

Sodium chloride also known as table salt has the chemical formula of NaCl. It is also known as Rock salt which is consumed by humans.

Balancing the given equation:

2Na ₊ Cl₂ → 2NaCl

Given:

The number of moles of chlorine = 1.25 moles

Number of NaCl formed :

1.25 mole Cl₂ ₓ 2 mole NaCl ÷ 1 mole Cl = 2.5 mole

Mass of sodium chloride formed :

2.5 mole NaCl × 58.44 g NaCl ÷ 1 mole NaCl = 146 g.

146 g sodium chloride is formed when 1.25 moles of chlorine reacts with excess sodium.

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A control group would be a good addition to this experiment. An experimental group that does not receive the same care as the experimental group is referred to as a control group.

In this scenario, a can without radiation would serve as the control group and a can with radiation as the experimental group. This would enable us to compare the outcomes of the two groups and determine whether the radiation affected the temperature in any way. Increasing the frequency of the temperature measurements would be another method to enhance this experiment.

We may take temperature readings every minute or every five minutes instead of every fifteen minutes. We would be able to track the temperature changes more precisely and receive more exact data as a result.

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The amount of heat required to vaporize 500g of the liquid at its boiling point is 7436.40 kJ.

To calculate the amount of heat required to vaporize 500g of the liquid, we need to use the following formula:

Q = m × ΔHvap

Where Q is the amount of heat required in kilojoules (kJ), m is the mass of the liquid in grams (g), and ΔHvap is the enthalpy of vaporization in kilojoules per mole (kJ/mol).

First, we need to convert the mass of the liquid from grams to moles:

moles = mass / molecular weight
moles = 500g / 27.5 g/mol
moles = 18.18 mol

Next, we can use the enthalpy of vaporization to calculate the amount of heat required to vaporize one mole of the liquid:

Q = ΔHvap × moles
Q = 22.5 kJ/mol × 18.18 mol
Q = 409.1 kJ

Finally, we can use the amount of heat required for one mole to find the amount of heat required for 500g:

Q = 409.1 kJ / mol × 18.18 mol
Q = 7436.4 kJ

Rounding up to the second decimal place, the amount of heat required to vaporize 500g of the liquid at its boiling point is 7436.40 kJ.

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Substances must have the same types of bonds before and after the reaction. In a spontaneous chemical reaction, the types of bonds in the reactants can change as the reaction proceeds, forming different bonds in the products.

Here's a brief explanation of the other options:
(b) The mass of the reactants is equal to the mass of the products. This statement is true due to the Law of Conservation of Mass, which states that mass is neither created nor destroyed in a chemical reaction. (c) Gibbs free energy is negative. This statement is true for spontaneous reactions, as a negative Gibbs free energy indicates that a reaction is thermodynamically favorable and will occur spontaneously under constant temperature and pressure.

(d) Energy is conserved. This statement is true due to the Law of Conservation of Energy, which states that energy cannot be created or destroyed, only converted from one form to another. In a chemical reaction, energy may be released or absorbed, but the total energy remains constant.

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The liquid described, containing 60% sugar and 40% water throughout its composition, is called a homogeneous mixture.

A homogeneous mixture is a type of mixture where the components are uniformly distributed throughout the mixture, resulting in a uniform composition and appearance. In a homogeneous mixture, the components are not visibly distinct and cannot be easily separated by physical means, such as filtering or settling.

Homogeneous mixtures can be either single-phase or multi-phase, depending on the number of components present and the nature of their interactions. Examples of homogeneous mixtures include solutions (such as saltwater), alloys (such as brass), and some types of gels and emulsions.

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On average, ocean water is slightly basic, with a pH level around 8.1. A pH level of 7 is considered neutral, while levels below 7 are acidic, and levels above 7 are basic.

Ocean water has a pH level that typically ranges between 7.5 and 8.5, making it slightly basic. A pH level of 7 is considered neutral, while levels below 7 are acidic, and levels above 7 are basic. The slightly basic nature of ocean water is due to the presence of various dissolved salts, predominantly sodium chloride.

However, factors such as pollution and increasing carbon dioxide levels can lower the pH, making the water more acidic. This process, called ocean acidification, has harmful effects on marine life, particularly species with shells or exoskeletons made of calcium carbonate, as the increased acidity can dissolve these structures.

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A low water fuel cutoff is a safety device that is commonly used in boilers to prevent the boiler from operating without sufficient water. The purpose of the low water fuel cutoff is to shut off the fuel supply to the burner when the water level in the boiler drops below a certain point, which can prevent damage to the boiler and ensure safe operation.

In a typical low water fuel cutoff system, a probe or sensor is installed in the boiler to detect the water level. If the water level drops below the set point, the sensor sends a signal to a control unit, which activates a switch that shuts off the fuel supply to the burner. The system may also include an alarm or other warning device to alert the operator to the low water condition.

Low water fuel cutoffs are required by law in many jurisdictions, and are an important safety feature in boiler operation. They can help prevent catastrophic boiler failures due to overheating and other issues that can occur when the water level in the boiler drops too low. It is important to ensure that the low water fuel cutoff system is properly installed, maintained, and tested regularly to ensure safe and reliable boiler operation.

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The resulting pressure of the gas above the liquid, given that the valve at the bottom of the container is opened, allowing all the liquid to be removed is 0.158 atm

From the question given above, the following data were obtained

Using the Boyle's law equation, we can obtain the new pressure of the gas as follow:

P₁V₁ = P₂V₂

1.58 × 0.125  = P₂ × 1.25

0.1975 = P₂ × 1.25

Divide both sides by 1.25

P₂ = 0.1975 / 1.25

P₂ = 0.158 atm

Thus, we can conclude the resulting pressure of the gas is 0.158 atm

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23.4 mL of 0.200 M potassium chloride solution should be added.

To solve this problem, we need to determine the limiting reagent and the amount of product that can be formed. From the balanced chemical equation, we know that the reaction between potassium chloride and lead(II) nitrate forms lead(II) chloride and potassium nitrate:

Pb(NO₃)₂ + 2KCl → PbCl₂ + 2KNO₃

We want to find out how much potassium chloride is needed to react with all of the lead(II) nitrate, so we need to figure out how much lead(II) ion is present in the 39.0 mL of 0.250 M lead(II) nitrate solution.

moles of Pb(NO₃)₂ = M × V = 0.250 mol/L × 0.0390 L

moles of Pb(NO₃)₂ = 0.00975 mol

Since the reaction requires two moles of KCl for each mole of Pb(NO₃)₂, we need:

moles of KCl = 0.00975 mol Pb(NO₃)₂ × 2 mol KCl/mol Pb(NO₃)₂

moles of KCl = 0.0195 mol KCl

Now we can use the molarity of the potassium chloride solution to find the volume required:

V = moles / molarity

V = 0.0195 mol / 0.200 mol/L

V = 0.0975 L

V = 97.5 mL

However, we need to add only enough potassium chloride solution to react with all of the lead(II) nitrate. Therefore, we only need to add 23.4 mL of 0.200 M potassium chloride solution to react completely with the lead(II) nitrate.

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Answer:

The reaction NH3(aq) + HNO3(aq) → NH4NO3(aq) is an acid-base reaction. In an acid-base reaction, an acid and a base react to form a salt and water. In this reaction, the acid is nitric acid (HNO3) and the base is ammonia (NH3). The salt that is formed is ammonium nitrate (NH4NO3).

The other choices are not correct. A precipitation reaction is a reaction in which a solid precipitate forms from a solution. A redox reaction is a reaction in which electrons are transferred between atoms or molecules. A decomposition reaction is a reaction in which a compound breaks down into two or more simpler substances.

Explanation:

John Heartfield's artwork "Have No Fear, He's a Vegetarian" is an example of political photomontage.

Photomontage is a technique of creating an image by combining multiple photographs or images.

Political photomontage is a type of photomontage that uses images and text to convey a political message or critique.

In the case of "Have No Fear, He's a Vegetarian," Heartfield combines an image of a pig's head with a photograph of a man, along with the text "Keine Hemmungen dieser Mann isst auch keine Wurst" (No inhibitions, this man doesn't eat sausage either).

The pig's head represents the brutal slaughter of animals for meat, and the man's face suggests that he is both sympathetic to animal rights and capable of resisting violence.

The text reinforces this message by asserting that the man is a vegetarian.

The artwork is a powerful critique of the fascist regime in Germany during the 1930s, which was characterized by violence, authoritarianism, and the glorification of meat-eating.

By using photomontage to create a visually striking and thought-provoking image, Heartfield was able to convey a complex political message in a way that resonated with many people at the time and continues to inspire and influence artists and activists today.

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The volume of Cl2 gas formed at 0.6 atm and 289K is 12.3 L. we first need to determine the molar mass of C2H2Cl4. The molar mass of C2H2Cl4 is 167.84 g/mol. The volume of Cl2 gas formed at 0.6 atm and 289K is 12.3 L.

To find the number of moles of C2H2Cl4, we divide the mass by the molar mass:

Number of moles of C2H2Cl4 = 51 g / 167.84 g/mol = 0.304 moles

According to the balanced chemical equation, 2 moles of Cl2 are required to produce 1 mole of C2H2Cl4. Therefore, the number of moles of Cl2 required to react with 0.304 moles of C2H2Cl4 is:

Number of moles of Cl2 = 2 × 0.304 moles = 0.608 moles

To calculate the volume of Cl2 gas formed at 0.6 atm and 289K, we can use the ideal gas law:

PV = nRT

where P is the pressure, V is the volume, n is the number of moles, R is the gas constant (0.0821 L·atm/mol·K), and T is the temperature in Kelvin.

We can rearrange this equation to solve for V:

V = nRT / P

Substituting the values, we get:

V = (0.608 moles) × (0.0821 L·atm/mol·K) × (289 K) / (0.6 atm) = 12.3 L

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The molecules with a net dipole moment are (CH₃)₂O and CH₂Cl₂.  (CH₃)₂O and CH₂Cl₂ have a net dipole moment due to their asymmetrical molecular structure and uneven distribution of electron density.

A molecule has a net dipole moment when there is an uneven distribution of electron density, resulting in a molecule with a positive and negative end. In BF₃, the boron trifluoride molecule has a trigonal planar structure with symmetrical electron distribution, resulting in no net dipole moment. CCl₄, carbon tetrachloride, has a tetrahedral structure with evenly distributed electron density, also resulting in no net dipole moment.

CO₂, carbon dioxide, is a linear molecule with symmetrical electron distribution, having no net dipole moment. In contrast, (CH₃)₂O (dimethyl ether) and CH₂Cl₂ (dichloromethane) have asymmetrical molecular structures, leading to uneven electron distribution and a net dipole moment.

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The given compound, (2S, 3R)-2-bromo-3-chlorobutane, has two chirality centers. This means that it has four possible stereoisomers, with each isomer having a different spatial arrangement of atoms around the two chirality centers.

The stereochemistry of a molecule is described using the R/S system, where R stands for rectus (Latin for right) and S stands for sinister (Latin for left). To determine the R or S configuration at each chirality center, we need to assign priorities to the four substituent groups based on atomic number. The group with the highest atomic number gets the highest priority, followed by the group with the next highest atomic number, and so on. If two or more groups have the same priority, we look at the next set of atoms until we find a point of difference.

In this compound, the bromine atom has the highest priority at the first chirality center, while the chlorine atom has the highest priority at the second chirality center. Once we have assigned priorities to all four substituent groups, we can determine the configuration at each center by visualizing the molecule with the lowest priority group (in this case, a methyl group) pointing away from us. If the three remaining groups are arranged in a clockwise direction, the configuration is labeled R, and if they are arranged counterclockwise, the configuration is labeled S.

Therefore, the four possible stereoisomers of (2S, 3R)-2-bromo-3-chlorobutane are (2S, 3R), (2S, 3S), (2R, 3R), and (2R, 3S). Each of these isomers has a unique three-dimensional structure and physical properties, despite having the same chemical formula.

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The balanced chemical equation for the reaction between calcium hydroxide (Ca(OH)2) and hydrochloric acid (HCl) is: Ca(OH)2 + 2HCl → CaCl2 + 2H2O

The balanced chemical equation tells us the stoichiometric ratio between the reactants and products.

In this case, we see that one mole of Ca(OH)2 reacts with two moles of HCl. This means that we need half as many moles of Ca(OH)2 as we have moles of HCl to completely neutralize the acid.

Therefore, to neutralize three moles of HCl, we need 1.5 moles of Ca(OH)2. This can be calculated using the ratio of the coefficients in the balanced equation.

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- Therefore the concentration of the HCl in the solution whose pH – 3 is 0.001 M.

When two reactant molecules possessing the necessary threshold energy collide with each other, they form an unstable activated complex or transition state. The given plot shows the energy diagram of an exothermic reaction.

In an exothermic reaction, the energy of the reactants is less than that of the products. The energy hump corresponds to the energy barrier existing between the reactants and products. The energy acquired by the reactant molecules to reach the level of threshold energy is called the activation energy.

1. 1st column on the lower left side = Reactants

2. Above that 2nd column = Eₐ = Activation energy of forward reaction

3. Above that 3rd column = Transition state

4. On the right upper part, 4th column = Enthalpy change ΔH

5. On the right lower part, 5th column = Products

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In radioactive decay, approximately 24.7 grams of Francium-223 would be left after 30 minutes. The correct answer is D. 24.7 grams.

To solve this problem, we can use the formula for radioactive decay:

N = N0 * (1/2)^(t/T)

where N is the amount of radioactive material at time t, N0 is the initial amount of radioactive material, T is the half-life, and t is the elapsed time.

Plugging in the given values, we get:

N = 60 * (1/2)^(30/22)

N ≈ 24.7

Therefore, approximately 24.7 grams of Francium-223 would be left after 30 minutes.

Alternatively, the half-life of Francium (Fr-223) is 22 minutes. Given that 60 grams is present now, after one half-life (22 minutes), 30 grams would be left. In 30 minutes, 8 more minutes would have passed after the first half-life. To find the amount left, we can use the formula:

Final amount = Initial amount * (1/2)^(time passed / half-life)

Final amount = 30 * (1/2)^(8/22) ≈ 24.7 grams

So, the correct answer is D. 24.7 grams.

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17.3 L is the volume of 201 g of mercury vapor at 822 K and 0.512 atm.

To solve this problem, we can use the ideal gas law: PV = nRT, where P is the pressure, V is the volume, n is the number of moles, R is the gas constant, and T is the temperature in Kelvin. We can rearrange this equation to solve for the volume:

V = nRT/P

First, we need to find the number of moles of Hg atoms in 201 g of mercury vapor. We can use the molar mass of mercury (200.59 g/mol) to convert from grams to moles:

n = 201 g / 200.59 g/mol = 1.001 mol

Next, we need to convert the temperature from Celsius to Kelvin:

T = 822 K

Finally, we can plug in the values for n, R (0.08206 L·atm/mol·K), P (0.512 atm), and T into the equation:

V = (1.001 mol) x (0.08206 L·atm/mol·K) x (822 K) / (0.512 atm) = 17.3 L

Therefore, the answer is E) 17.3 L.

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To find the concentrations at equilibrium, we need to know the reaction's balanced chemical equation and the equilibrium constant (K) for the reaction.

The concentrations at equilibrium depend on the balanced chemical equation for the reaction and the equilibrium constant (K). The balanced chemical equation allows us to determine the stoichiometry, while the equilibrium constant (K) indicates the ratio of products to reactants at equilibrium.

First, write down the balanced chemical equation and determine the stoichiometry. Then, set up an ICE (Initial, Change, Equilibrium) table using the initial concentrations of reactants and products. Apply the equilibrium constant expression (K) by relating the concentrations of products and reactants at equilibrium, and solve for the unknown equilibrium concentrations.

Without the balanced chemical equation and the equilibrium constant (K), we cannot calculate the specific concentrations at equilibrium.

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Answer:

B) 2.86 atm

In order to calculate this, you have to use the Henry's law which is:

C= kP

C = concentration of a dissolved gas

k = Henry's Law constant

P = partial pressure of the gas

C = kP

1.05x10^-5 M = k(0.00030 atm)

When we solve for k, we get:

k = (1.05x10^-5 M) / (0.00030 atm)

k = 3.50x10^-2 M/atm

We can now apply Henry's rule to calculate the partial pressure of carbon dioxide that will result in a concentration of 100.0 mg/L (or 0.1 g/L) in water:

0.1 g/L = (3.50x10^-2 M/atm)P

When we convert units, we get:

0.1 g/L = (3.50x10^-2 mol/L)P

P = (0.1 g/L) / (3.50x10^-2 mol/L)

P = 2.86 atm

The name of the complex ion ZnCl2(en)2 is "dichloridobis(ethane-1,2-diamine)zinc(II)".

Here's how the name is derived:

The complex contains the metal ion zinc, which has a +2 oxidation state, so we use the Roman numeral (II) to indicate this in the name.

The complex contains two chloride ions, which are named as "dichlorido" since there are two of them.

The complex also contains two molecules of ethane-1,2-diamine, which is abbreviated as "en". The two en ligands are named using the prefix "bis".

Therefore, the complete name of the complex ion is "dichloridobis(ethane-1,2-diamine)zinc(II)".

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The heat evolved during a neutralization reaction is dependent on the strength of the acid and base being used. HCl is a stronger acid than CH3COOH, meaning it requires more energy to break the H-Cl bond.

NaOH is a strong base and will fully dissociate to release OH- ions, which will react with the H+ ions from the acid to form water. This reaction will release more heat for HCl than CH3COOH due to the stronger bond in HCl. This result was expected as HCl is a stronger acid than CH3COOH. The stronger the acid, the more heat is released during the reaction with a strong base.

The heat evolved during the neutralization of HCl with NaOH is greater than that for CH3COOH with NaOH because HCl is a strong acid while CH3COOH is a weak acid. In the reaction between a strong acid and a strong base like NaOH, the ions dissociate completely, resulting in a higher amount of heat being released. On the other hand, weak acids like CH3COOH do not fully dissociate, so fewer ions are available to react with the base, leading to a smaller amount of heat released. This outcome should be expected based on the differences in strength between the two acids.

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The amount of heat released in kJ when 75 grams of phosphorus react with excess chlorine is 858.848 kJ.

Moles of P = mass of P / molar mass of P = 75 g / 30.97 g/mol = 2.42 moles

From the balanced chemical equation, 2 moles of P react with 5 moles of Cl2 to form 2 moles of PCl5.

Moles of PCl5 = (2.42 moles P / 2 moles PCl5) x (2 moles PCl5 / 5 moles Cl2) = 0.968 moles

Heat released = moles of PCl5 x AH° = 0.968 moles x (-886 kJ/mol) = 858.848 kJ

In other words, the amount of heat released in kJ when 75 grams of phosphorus react with excess chlorine is approximately 858.848 kJ.

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The mass percent of chlorine in CCl3F is 77.4%.

The molar mass of CCl3F is:

To calculate the mass percent of chlorine in CCl3F (Freon-11), we need to determine the molar mass of chlorine and the molar mass of the entire compound.

CCl3F = 1xC + 3xCl + 1xF = 1x12.01 + 3x35.45 + 1x18.99 = 137.37 g/mol

The mass percent of chlorine in CCl3F can be calculated as:

Mass of chlorine / Mass of CCl3F x 100%

Mass of chlorine = 3 x atomic mass of Cl = 3 x 35.45 = 106.35 g

Mass of CCl3F = 137.37 g

Mass percent of chlorine in CCl3F = 106.35 g / 137.37 g x 100% = 77.4%

Therefore, the mass percent of chlorine in CCl3F is 77.4%.

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