A student is analyzing an unknown compound made only of carbon, hydrogen, and oxygen. She burns 1.246 g of the unknown and recovers 1.823g of CO2. She also recovers and analyzes the resulting water from the combustion.  Determine the mass, in grams, of carbon in the 1.246 g sample of the compound. Her analysis of the water vapor reveals that hydrogen is 6.727% of the total compound. Determine the mass, in grams of hydrogen in the original 1.246 g sample.  Determine the empirical formula of the unknown compound. Using a mass spectrometer, the molecular mass is determined to be 180. g/mol. What is the molecular formula of the unknown compound?  Show your work. Note: Your answer(s) must be provided in this text box. If you are unable to show your work adequately using the Rich Text Editor, complete your work on scratch paper. Upload a photo of your work in the “Comments” of this exam immediately after you have completed and submitted the exam. You can access the “Comments” through the grade book. Answers on scratch paper alone will not be scored.

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 calibrated line in the chart. The figure presents a graph consisting of five points and a straight line of best fit. The horizontal axis is labeled “Mass of C a C O 3, solid, in grams,” and the numbers 0.05 through 0.20, in increments of 0.05, are indicated. The vertical axis is labeled “Pressure of Gas Produced, in atmospheres,” and the numbers 0.02 through 0.10, in increments of 0.01, are indicated. The data represented in the graph are as follows. Note that all values are approximate. The line begins at a mass of 0.06 gram and a pressure of 0.03 atmosphere, and ends at a mass of 0.21 gram and a pressure of 0.10 atmosphere. The data points are at 0.07 gram and 0.032 atmosphere; 0.09 gram and 0.045 atmosphere; 0.14 gram and 0.068 atmosphere; 0.17 gram and 0.08 atmosphere; and 0.20 gram and 0.096 atmosphere. The experiment is repeated with an eggshell sample, and the experimental data are recorded in the table. Mass of eggshell sample 0.200 g Pressure prior to reaction 0.800 atm Pressure at completion of reaction 0.870 atm   Which of the following equations best represents the species that react and the species that are produced when CaCO3(s) and HCl(aq) are combined?

The figure presents C H 4 and O 2 gas molecules in a vessel. There is a key that shows that a small unshaded circle represents H, a larger dark shaded circle represents C, and a lightly shaded circle represents O. In the mixture there are 2 C H 4 molecules and 6 O 2 molecules. The reactants represented above are placed in a vessel and a reaction occurs. Which of the following best represents the contents of the vessel after the reaction has proceeded as completely as possible?

For an experiment, a student needs 100.0 mL of 0.4220 M NaCl. If the student starts with NaCl(s) and distilled water, which of the following pieces of laboratory glassware should the student use to prepare the solution with the greatest accuracy?

The molecular formula and molar mass of two straight-chain hydrocarbons are listed in the table below. Based on the information in the table, which compound has the higher boiling point, and why is that compound’s boiling point higher?   Name Molecular Formula Molar Mass (g/mol) Ethane C2H6 30 Butane C4H10 58

Use the values calculated in Step 5 to calculate the mass percent of Cu in the brass sample using both experimental techniques. 

MnO4− + 5 Fe2+ + 8 H+ → Mn2+ + 5 Fe3+ + 4 H2O In the reaction represented above, the number of MnO4- ions that react must be equal to which of the following?

When water is added to a mixture of Na2O2(s) and S(s) , a redox reaction occurs, as represented by the equation below.   2 N a 2 O 2 solid plus S solid plus 2 H 2 O liquid react to form 4 N a O H aqueous plus S O 2 aqueous   delta H naught at 298 equals negative 610 kilojoules per mole of reaction. delta S naught at 298 equals negative 7.3 joules per open parenthesis kelvin times mole of reaction close parenthesis   Atoms of which element are reduced in the reaction?

10 HI + 2 KMnO4 + 3 H2SO4 → 5 I2 + 2 MnSO4 + K2SO4 + 8 H2O According to the balanced equation above, how many moles of HI would be necessary to produce 2.5 mol of I2, starting with 4.0 mol of KMnO4 and 3.0 mol of H2SO4 ?

When the actual gas volume is greater than the volume predicted by the ideal gas law, the explanation lies in the fact that the ideal gas law does NOT include a factor for molecular.