Question

An experiment is performed to measure the mass percent of CaCO3(s) in eggshells. Five different samples of CaCO3(s) of known mass react with an excess of 2.0 M HCl(aq) in identical sealed, rigid reaction vessels. The pressure of the gas produced is measured with a pressure gauge attached to the reaction vessel. Since the reaction is exothermic, the reaction system is cooled to its original temperature before the pressure is recorded. The experimental data are used to create the calibration line in the figure. The experiment is repeated with an eggshell sample, and the experimental data are recorded in the table below.

Mass of eggshell sample 0.200 g Pressure prior to reaction 0.800 atm Pressure at completion of reaction 0.870 atm The mass percent of CaCO3(s) in the eggshell sample is closest to Group of answer choices: 30% 60% 45% 75%

Answer 1

To determine the mass percent of CaCO3 in the eggshell sample, use the ideal gas law and the reaction between CaCO3 and HCl. Calculate the number of moles of CO2 gas produced and the mass of CaCO3, then calculate the mass percent of CaCO3 in the eggshell sample.

To determine the mass percent of CaCO3 in the eggshell sample, we can use the ideal gas law and the reaction between CaCO3 and HCl. The equation for the reaction is:

CaCO3(s) + 2HCl(aq) -> CaCl2(aq) + H2O(l) + CO2(g)

First, we need to calculate the number of moles of CO2 gas produced. Using the ideal gas law, we can calculate the moles of CO2:

moles of CO2 = (pressure of CO2 * volume of reaction vessel) / (gas constant * temperature)

Next, we can determine the mass of CaCO3 by using the molar mass of CaCO3:

mass of CaCO3 = moles of CO2 * molar mass of CaCO3

Finally, we can calculate the mass percent of CaCO3 in the eggshell sample:

mass percent of CaCO3 = (mass of CaCO3 / mass of eggshell sample) * 100%