4.00-g sample of a mixture of CaO and BaO is placed in a 1.00-L vessel containing CO2 gas at a pressure of 730 torr and a temperature of 25°C. The CO2 reacts with the CaO and BaO, forming CaCO3 and BaCO3. When the reaction is complete, the pressure of the remaining CO2 is 150 torr. b. Calculate the mass percentage of CaO in the mixture.

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Convert the initial and final pressures of CO2 from torr to atmospheres for easier calculation. Recall that 1 atm = 760 torr.

Calculate the initial moles of CO2 using the ideal gas law, PV = nRT. Use the converted pressure in atmospheres, the volume of the vessel (1.00 L), and the temperature in Kelvin (25°C + 273.15). R is the ideal gas constant, 0.0821 L atm/mol K.

Repeat the calculation for the final moles of CO2 using the final pressure after the reaction.

Determine the moles of CO2 that reacted by subtracting the final moles of CO2 from the initial moles of CO2.

Assuming the reaction goes to completion and each mole of CaO and BaO reacts with one mole of CO2, use the stoichiometry of the reactions CaO + CO2 → CaCO3 and BaO + CO2 → BaCO3 to find the moles of CaO in the mixture. Then, calculate the mass of CaO using its molar mass (56.08 g/mol) and express it as a percentage of the total mass of the mixture (4.00 g).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Stoichiometry

Stoichiometry is the calculation of reactants and products in chemical reactions based on the balanced chemical equations. It allows us to determine the relationships between the quantities of substances involved in a reaction, which is essential for solving problems related to mass and moles. In this question, stoichiometry will help us relate the amounts of CaO and BaO to the amount of CO2 consumed.

Gas Laws

Gas laws describe the behavior of gases in relation to pressure, volume, and temperature. The ideal gas law (PV=nRT) is particularly useful for calculating the number of moles of gas present under specific conditions. In this scenario, understanding how the pressure of CO2 changes before and after the reaction is crucial for determining how much CO2 reacted with the metal oxides.

Mass Percentage

Mass percentage is a way of expressing the concentration of a component in a mixture as a percentage of the total mass. It is calculated by dividing the mass of the component by the total mass of the mixture and multiplying by 100. In this problem, calculating the mass percentage of CaO requires determining the mass of CaO in relation to the total mass of the mixture of CaO and BaO.

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An herbicide is found to contain only C, H, N, and Cl. The complete combustion of a 100.0-mg sample of the herbicide in excess oxygen produces 83.16 mL of CO2 and 73.30 mL of H2O vapor expressed at STP. A separate analysis shows that the sample also contains 16.44 mg of Cl. (b) Calculate its empirical formula.

Textbook Question

An herbicide is found to contain only C, H, N, and Cl. The complete combustion of a 100.0-mg sample of the herbicide in excess oxygen produces 83.16 mL of CO₂ and 73.30 mL of H₂O vapor expressed at STP. A separate analysis shows that the sample also contains 16.44 mg of Cl. (c) What other information would you need to know about this compound to calculate its true molecular formula?

Textbook Question

Ammonia and hydrogen chloride react to form solid ammonium chloride: NH31g2 + HCl1g2¡NH4Cl1s2 Two 2.00-L flasks at 25 °C are connected by a valve, as shown in the drawing. One flask contains 5.00 g of NH31g2, and the other contains 5.00 g of HCl(g). When the valve is opened, the gases react until one is completely consumed. (a) Which gas will remain in the system after the reaction is complete?

Textbook Question

Ammonia and hydrogen chloride react to form solid ammonium chloride: NH₃(g) + HCl(g) → NH₄Cl(s)

Two 2.00-L flasks at 25 °C are connected by a valve, as shown in the drawing. One flask contains 5.00 g of NH₃(g), and the other contains 5.00 g of HCl(g). When the valve is opened, the gases react until one is completely consumed. (b) What will be the final pressure of the system after the reaction is complete? (Neglect the volume of the ammonium chloride formed.)

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