Which would show an example of how physical changes are reversible ?

The molar mass of the solute is calculated by first finding the molality of the solution using the freezing point depression, then using this to find the number of moles of solute, and finally dividing the mass of the solute by the number of moles. The computed molar mass of the solute is 62.15 g/mol.

To calculate the molar mass of the solute, we first need to calculate the molality of the solution using the freezing point depression formula, ΔTf = iKfm, where i is the van't Hoff factor (which is 1 for a non-electrolyte), Kf is the freezing point depression constant for water (1.86°C/m), and m is molality. We know that ΔTf = -1.23°C. So, molality can be determined as follows: m = ΔTf / (i x Kf) = -1.23°C / (1 x 1.86°C/m) = -0.66mol/kg.

Molality is defined as moles of solute per kilogram of solvent. Therefore, if we multiply the molality by the mass of the solvent (105g or 0.105kg), we get the moles of solute. Moles of solute = m x mass of solvent = -0.66mol/kg x 0.105kg = -0.0693mol.

Finally, to determine the molar mass of the solute, we divide the mass of the solute by the number of moles. Molar mass = mass of solute / moles of solute = 4.305g / -0.0693mol = -62.15g/mol. The negative sign indicates a freezing point depression, but the molar mass of a substance cannot be negative. Therefore, the molar mass of the solute is 62.15g/mol.

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Methanol is the most plausible candidate among these potential contaminants because its oxygen content is closest to the reported mass percent of oxygen in the sample (49.7%).

The proportional amount of a certain component (typically a substance or element) in a combination, compound, or solution is expressed as mass percent (also known as weight percent or weightage). It is a percentage that represents the component's mass in relation to the overall mass of the combination, compound, or solution multiplied by 100.

molecular formula mass of [tex]\rm C_6H_{12}O_6[/tex] = 180.18 g/mol

mass percent of oxygen is

(96.00 g/mol / 180.18 g/mol) × 100%

≈ 53.3%

In water, the mass percent of oxygen is:

(16.00 g/mol / 18.02 g/mol) × 100%

≈ 88.9%

In formaldehyde, the mass percent of oxygen is:

(16.00 g/mol / 30.03 g/mol) × 100%

≈ 53.3%

In methanol, the mass percent of oxygen is:

(16.00 g/mol / 32.04 g/mol) × 100%

≈ 50.0%

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When a liquid boils, energy is absorbed, and potential energy increases.

The energy changes associated with a liquid boiling are:

Boiling involves supplying energy to break intermolecular forces and convert the liquid into a gas, leading to an increase in potential energy.

During boiling, energy is absorbed to convert the liquid into gas, increasing the potential energy of the molecules. The temperature remains constant as energy is used for the phase change. The correct answer is B.

A liquid changes phases from a liquid to a gas as it boils. This process is associated with the absorption of energy. Specifically, energy in the form of heat is absorbed by the liquid to overcome the intermolecular forces that hold the molecules together. The molecules' potential energy rises as a result.

An example of this can be seen when water boils. When you heat water on a stove, the temperature rises until it reaches [tex]100^{\circ}C[/tex] ([tex]212^{\circ}F[/tex]). At this boiling point, the water does not get hotter. Instead, the energy absorbed continues to be used to convert the water from liquid to vapor, indicating that the energy is going into increasing the potential energy.

Approximately 21.4 kJ of energy is needed to convert 64.0 grams of ice at 0.00°C to liquid water at the same temperature. This is calculated using the concept of 'enthalpy of fusion', which is the energy required to convert a substance from solid to liquid without changing its temperature.

To find out how much energy is needed to convert 64.0 grams of ice at 0.00°C to water at the same temperature, we should first understand that the melting of ice is an endothermic process, meaning it requires energy. The energy required to convert a substance from solid to liquid state without changing its temperature is termed the enthalpy of fusion.

For water, the enthalpy of fusion is 334 kJ/kg. However, our given mass is in grams, so we need to convert it to kilograms, thus we have 0.064 kg of ice. Using the formula Q=mLf (where Q is energy, m is mass, and Lf is the enthalpy of fusion), we can calculate the necessary energy: Q = (0.064 kg)(334 kJ/kg) = 21.376 kJ.

So, approximatley 21.4 kJ of energy is required to convert 64.0 grams of ice at 0.00°C into water at the same temperature.

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Final answer:

The molarity of NaOH in the titration with 50ml of 0.2M HCl when it takes 40ml of NaOH to reach the equivalence point is calculated using the formula M1V1 = M2V2. The resulting molarity of NaOH is 0.25M.

Explanation:

The student is asking about a titration question, specifically determining the molarity of a sodium hydroxide (NaOH) solution based on its reaction with a known concentration of hydrochloric acid (HCl).

To calculate the molarity (M) of NaOH, we can use the formula:

M1V1 = M2V2, where:

Given that we have 50ml of 0.2 M HCl and it takes 40ml of NaOH to reach the equivalence point, we can solve for M2 (molarity of NaOH) as follows:

(0.2 M) * (50 ml) = (M2) * (40 ml)

M2 = (0.2 M * 50 ml) / 40 ml

M2 = 0.25 M

Therefore, the molarity of NaOH is 0.25 M.

Answer: The mass percent of NaCl solution is 16.66 %

Explanation:

To calculate the mass percentage of NaCl solution, we use the equation:

[tex]\text{Mass percent of NaCl solution}=\frac{\text{Mass of solute (NaCl)}}{\text{Mass of solution}}\times 100[/tex]

Mass of solute (NaCl) = 500.0 g

Mass of solvent (water) = 2.50 kg = 2500 g    (Conversion factor: 1 kg = 1000 g)

Mass of solution = Mass of solute + Mass of solvent = 500.0 + 2500 = 3000 g

Putting values in above equation, we get:

[tex]\text{Mass percent of NaCl solution}=\frac{500.0g}{3000g}\times 100\\\\\text{Mass percent of NaCl solution}=16.66\%[/tex]

Hence, the mass percent of NaCl solution is 16.66 %

Solubility product constant (Ksp) is applied to the saturated ionic solutions which are in equilibrium with its solid form. The solid is partially dissociated into its ions.

For the BaF, the dissociation as follows;
BaF₂(s) ⇄ Ba²⁺(aq) + 2F⁻(aq)

Hence,
        Ksp = [Ba²⁺(aq)] [F⁻(aq)]²

he is right he is correct

Answer:

Sodium chloride, regular table salt, is also known as the mineral halite. The diagram to the right shows how sodium and chlorine atoms pack tightly together to form cube-like units of the compound NaCl

Explanation:

Answer : Any natural sources of CFC's are not known only the major sources like aerosols, propellants, refrigerants,etc are known. So, if any natural sources are given then it cannot be called as a major source for emitting CFC into environment.

Answer:

• televisions

Final answer:

H2O gains a proton to become H3O+, which makes it a Brønsted-Lowry base in that reaction. However, water can also behave as a Brønsted-Lowry acid in other reactions, where it is the proton donor.

Explanation:

When H2O transforms into H3O+, it gains a proton, evidenced by the increase in hydrogen atoms. This process classifies water (H2O) as a Brønsted-Lowry base in this specific scenario, as it is accepting a proton. However, it's important to note that water can also act as a Brønsted-Lowry acid under different conditions, donating a proton to another substance.

For instance, in the reaction C6H5NH₂(aq) + H₂O(l) → C6H5NH3*(aq) + OH−(aq), water donates a proton to C6H5NH2, making it the Brønsted-Lowry acid. Conversely, in the reaction HCOOH(aq) + H2O(l) → H3O*(aq) + HCOO−(aq), water accepts a proton from formic acid (HCOOH), making it the Brønsted-Lowry base.

To neutralize 1.0 liter of 0.50 M HCl, you need 3.011 × 10²³ of hydroxide (OH⁻) ions.

To determine how many hydroxide ions are needed to completely neutralize 1.0 liter of 0.50 M HCl, follow a simple stoichiometry process:

        HCl + OH⁻ → H₂O + Cl⁻

Given:

First, calculate the moles of HCl in the solution:

Moles of HCl = Molarity × Volume = 0.50M × 1.0L = 0.50moles

Since each mole of HCl provides one mole of H⁺ ions, there are 0.50 moles of H⁺ ions.

To completely neutralize these H⁺ ions, we need an equal number of OH⁻ ions:

Since 1 mole of any substance contains Avogadro's number of entities (ions, molecules, etc.), which is approximately 6.022 x 10²³ entities per mole, we can convert moles of OH⁻ to number of ions:

Number of OH⁻ ions = 0.50moles x 6.022 x 10²³ ions/mole = 3.011 x 10²³

The all substances that participate in the reaction are in gaseous phase and the given data are the concentrations when the reaction at equilibrium. Hence, we can use that given concentrations directly to find out the equilibrium constant, Kc.

The balanced equation for the equilibrium is,

                 2SO₂(g) + O₂(g) ⇄ 2SO₃(g)

Kc = [SO₃(g)]² / [SO₂(g)]² [O₂(g)]
Kc = (4 mol/L)² / (2 mol/L)² (1 mol/L)
Kc = 4 mol⁻¹ L

Hence, the equilibrium constant is 4 mol⁻¹ L

The element that has a ground-state electron configuration of [ar]4s23d104p5  - bromine (br)

Electron configurations are the representation of the electrons are around a nucleus.

Thus, the element that has a ground-state electron configuration of [ar]4s23d104p5  - bromine (br)

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HDPE has a density greater or equal to 0.941 g/cm³, which is less dense than water at 1 g/cm³, allowing it to float. LDPE has a lower density of 0.910-0.940 g/cm³, which is even less dense and more flexible than HDPE.

Density of HDPE vs Water

The density of high-density polyethylene (HDPE) relative to water is an interesting comparison, especially considering the applications of HDPE in various products. HDPE is defined by a density greater or equal to 0.941 g/cm³. It has a low degree of branching, resulting in stronger intermolecular forces due to the mostly linear molecules packing together well. Consequently, HDPE has a higher tensile strength and is used in items like milk jugs, detergent bottles, and water pipes. On the other hand, water has a density of approximately 1 g/cm³ at 4°C, which is in a liquid state. Since HDPE is less dense than water, it is capable of floating when formed into items like plastic bottles.

By contrast, low-density polyethylene (LDPE), with a density range of 0.910-0.940 g/cm³, characterizes materials that require greater flexibility and less strength, such as plastic bags and film wrap. It's important to recognize the unique properties of polymers like HDPE and LDPE and how their densities relate to their function in everyday materials.

The mass of aluminum, the heat energy equation Q = mcΔT is used with the given values, resulting in a calculated mass of 12 grams.

The mass of aluminum using the given energy, temperature change, and specific heat capacity, we employ the formula for heat transfer: Q = mcΔT, where Q is the heat energy, m is the mass, c is the specific heat capacity, and ΔT is the change in temperature.

Given that Q = 216 J, c = 0.90 J/°C·g, and ΔT = (35 - 15)°C = 20°C, we can rearrange the equation to solve for m:

m = Q / (cΔT) = 216 J / (0.90 J/°C·g · 20°C) = 216 J / (18 J/g) = 12 g

Therefore, the mass of aluminum is 12 grams.