Recent questions in Chemistry

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1 answer 66 views

A student needs to prepare 500 mL of a buffer solution with a pH of 7.5 using a weak acid HA and its conjugate base A-. HA has a pKa of 4.5 and its initial concentration is 0.2 M. What mass of HA and A- should be mixed to prepare the buffer solution?

asked Jan 22 in Chemical reactions by FernFlower71 (170 points)

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1 answer 67 views

A student needs to find the enthalpy of polymerization of ethylene from the enthalpies of combustion of ethylene gas (-1411 kJ/mol) and polyethylene (-5120 kJ/mol). Calculate the enthalpy change, in kJ/mol, for the polymerization of ethylene gas to form polyethylene.

asked Jan 22 in ThermoChemistry by BlairH599552 (230 points)

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1 answer 78 views

A student needs to find out how much heat is released or absorbed when 100 mL of 0.1 mol/L solution of barium chloride (BaCl2) is mixed with 150 mL of 0.1 mol/L solution of sodium sulfate (Na2SO4) at 25°C. Given the enthalpy of precipitation of BaSO4 as -256 kJ/mol, calculate the enthalpy change (in kJ) for the reaction that occurs and determine whether the reaction is exothermic or endothermic.

asked Jan 22 in ThermoChemistry by OpheliaTuggl (510 points)

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1 answer 76 views

A student needs to determine the standard electrode potential for the following reaction: Fe3+ + e- → Fe2+ Using the standard electrode potentials of Fe3+/Fe2+ and Ag+/Ag, calculate the standard cell potential for the following reaction: 2Ag+ (aq) + Fe(s) → 2Ag(s) + Fe2+ (aq) Determine if this reaction is spontaneous or nonspontaneous under standard conditions.

asked Jan 22 in ElectroChemistry by ScotBarcenas (230 points)

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1 answer 84 views

A student needs to determine the mass of silver that can be deposited on a silver electrode using a current of 2.5 A for 3 hours in a solution containing 0.2 M silver ions. What is the mass of silver deposited on the electrode? (Assuming 100% current efficiency and atomic weight of silver is 107.9 g/mol)

asked Jan 22 in ElectroChemistry by DarbyManske (290 points)

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1 answer 56 views

A student needs to determine the enthalpy change of a chemical reaction using the Hess's Law equation. They have the following information:- The enthalpy change for Reaction 1 is -210 kJ/mol- The enthalpy change for Reaction 2 is -325 kJ/mol- The enthalpy change for Reaction 3 is 155 kJ/molThe student needs to use Hess's Law to calculate the enthalpy change for the following reaction:4A + 3B → 2CGiven the information above, what is the enthalpy change for the reaction?

asked Jan 22 in Chemical reactions by MarilouMarco (370 points)

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1 answer 71 views

A student needs to determine the enthalpy change (ΔH) for the reaction between ammonium nitrate (NH4NO3) and water (H2O) using Hess's Law calculations. Given the following information: - ΔHf° (NH4NO3) = -365.4 kJ/mol- ΔHf° (HNO3) = -207.3 kJ/mol- ΔHf° (NH4+) = -132.5 kJ/mol- ΔHf° (NO3-) = -206.1 kJ/mol- ΔHf° (H2O) = -285.83 kJ/molFormulate the thermochemical equation for the reaction by using the given data and Hess's Law calculations, and then calculate the enthalpy change for the reaction.

asked Jan 22 in ThermoChemistry by FranKinchen (430 points)

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1 answer 65 views

A student needs to determine the diffusion coefficient of a gas in a liquid by measuring the rate of diffusion using a diffusion cell. If the student knows the initial concentration and final concentration of the gas in the cell, and the time it took for diffusion to occur, what is the diffusion coefficient of the gas in the liquid?

asked Jan 22 in Physical Chemistry by JuanBrain990 (150 points)

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1 answer 61 views

A student needs to determine the diffusion coefficient of a gas at a given temperature and pressure using Graham's law of diffusion. The student has the necessary equipment to measure the rate of diffusion of the gas and the molecular weight of the gas is known. Determine the diffusion coefficient of the gas.

asked Jan 22 in Physical Chemistry by WiltonVeitch (230 points)

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1 answer 74 views

A student needs to determine the concentration of a sulfuric acid solution using a sodium hydroxide solution of known concentration. The student performs a titration and records that it took 27.5 milliliters of the sodium hydroxide solution to neutralize 25 milliliters of the sulfuric acid solution. What is the concentration (in moles per liter) of the sulfuric acid solution?

asked Jan 22 in Chemical reactions by Mirta9018813 (370 points)

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1 answer 53 views

A student needs to determine the change in enthalpy (ΔH) for the reaction between methane (CH4) and oxygen (O2) to form carbon dioxide (CO2) and water (H2O) at a temperature of 25°C and a pressure of 1 atm. The initial concentrations of CH4 and O2 are both 0.1 M, and the final concentrations of CO2 and H2O are both 0.05 M. What is the change in enthalpy for this reaction at the given conditions?

asked Jan 22 in Physical Chemistry by Eli39B708868 (270 points)

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1 answer 59 views

A student needs to determine the amount of copper present in a sample of brass using coulometry. If the sample is dissolved in acid and subjected to coulometric analysis using a standard silver electrode, what is the concentration of copper (in ppm) in the brass sample?

asked Jan 22 in Analytical Chemistry by HermelindaAn (350 points)

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1 answer 11 views

A student needs to determine the activation energy for the electrochemical reaction between zinc and copper sulfate using the Arrhenius equation. The student has experimental data that includes the rate constants and temperatures at which the reaction was performed. Using the experimental data, the student needs to calculate the activation energy for the reaction and explain the significance of this value in terms of the reaction kinetics.

asked Jan 22 in ElectroChemistry by EssieHimes15 (350 points)

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1 answer 54 views

A student needs to determine the activation energy for an electrochemical reaction involving the oxidation of Zinc using a voltage of 1.85V, a current of 0.25A and a temperature of 25°C. Given that the standard potential for this reaction at 25°C is -0.76V, what is the activation energy of the reaction?

asked Jan 22 in ElectroChemistry by KatharinaGlo (390 points)

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1 answer 71 views

A student needs to calculate the Tafel slopes for the anodic and cathodic reactions from a given set of experimental data obtained during an electrochemical experiment. The experiment involves the corrosion of iron in a solution with a pH of 3.5. The anodic and cathodic current densities were measured at various applied potentials ranging from -700 mV vs SHE to -400 mV vs SHE. The student needs to plot a Tafel plot for each reaction and calculate their corresponding Tafel slopes. Based on the obtained results, the student needs to explain the corrosion mechanism of iron in the given acidic solution.

asked Jan 22 in ElectroChemistry by HesterGonsal (470 points)

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1 answer 52 views

A student needs to calculate the standard potential of a electrochemical cell formed by a zinc electrode and a silver electrode. The concentration of Zn2+ ions in the zinc half-cell is 1.0 M and the concentration of Ag+ ions in the silver half-cell is 0.1 M. The measured potential of the cell is 1.95 V. What is the standard potential of the cell?

asked Jan 22 in Physical Chemistry by FlorianRico (330 points)

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1 answer 100 views

A student needs to calculate the standard enthalpy of formation of magnesium oxide, MgO, using Hess's Law. The student has access to the following reactions and their corresponding enthalpy changes:1. Mg(s) + 1/2O2(g) → MgO(s) ΔH = -601.8 kJ/mol2. Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g) ΔH = -450.7 kJ/mol3. H2(g) + 1/2O2(g) → H2O(l) ΔH = -285.8 kJ/molWhat is the standard enthalpy of formation of MgO from its elements?

asked Jan 22 in ThermoChemistry by FriedaGreine (210 points)

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1 answer 58 views

A student needs to calculate the standard enthalpy change of combustion for propane using Hess's Law. They have the following information: C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(l) ΔH° = -2220 kJ/mol 2H2(g) + O2(g) → 2H2O(l) ΔH° = -484 kJ/mol 3C(s) + 2H2(g) → C3H8(g) ΔH° = +51 kJ/mol What is the standard enthalpy change of combustion for propane?

asked Jan 22 in ThermoChemistry by KaceyBannerm (350 points)

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1 answer 56 views

A student needs to calculate the standard cell potential for the following reaction at 25°C:Zn (s) + Fe2+ (aq) → Zn2+ (aq) + Fe (s)Given:- Standard reduction potentials: Eº(Zn2+/Zn) = -0.76 V and Eº(Fe2+/Fe) = -0.44 V- Concentration of Fe2+ = 0.1 M and concentration of Zn2+ = 1.0 MWhat is the value of the standard cell potential for this reaction?

asked Jan 22 in Physical Chemistry by EmiliaOddo6 (170 points)

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1 answer 104 views

A student needs to calculate the resistance of an electrochemical cell that has a concentration of 0.1 M for both copper(II) and zinc(II) ions, using an electrochemical sensor that measures 2.5 volts for the cell. Calculate the resistance of the electrochemical cell at room temperature, given that the Faraday constant is 96485 C/mol and the gas constant is 8.314 J/(mol·K).

asked Jan 22 in ElectroChemistry by BridgetMorri (210 points)

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