Sometimes in lab we collect the gas formed by a chemical reaction over water (see sketch at right). This makes it easy to isolate and measure the amount of gas produced. Suppose the H₂ gas evolved by a certain chemical reaction taking place at 50.0 °C is collected over water, using an apparatus something like that in the sketch, and the final volume of gas in the collection tube is measured to be 36.2 mL. 8 g x²² collected x gas Sketch of a gas-collection apparatus Calculate the mass of H₂ that is in the collection tube. Round your answer to 2 significant digits. You can make any normal and reasonable assumption about the reaction conditions and the nature of the gases. water y chemical reaction

Pyruvic acid, HC3H3O3, is involved in cell metabolism. It can be assayed for (that is, the amount of it determined) by using a yeast enzyme. The enzyme makes the following reaction go to completion: HC3H3O3(aq)C2H4O(aq)+CO2(g) If a sample containing pyruvic acid gives 21.2 mL of carbon dioxide gas, CO2, at 349 mmHg and 30C, how many grams of pyruvic acid are there in the sample?

A mixture contained zinc sulfide, ZnS, and lead sulfide, PbS. A sample of the mixture weighing 6.12 g was reacted with an excess of hydrochloric acid. The reactions are ZnS(s)+2HCL(aq)ZnCl2(aq)+H2S(g)PbS(s)+2HCL(aq)PbCl2(aq)+H2S(g) If the sample reacted completely and produced 1.049 L of hydrogen sulfide, H2S, at 23C and 762 mmHg, what were the percentages of ZnS and PbS in the mixture?

You have a gas, one of the three known phosphorus-fluorine compounds (PF3, PF3, and P2F4). To find out which, you have decided to measure its molar mass. (a) First, yon determine that the density of the gas is 5.60 g/L at a pressure of 0.971 atm and a temperature of 18.2 C. Calculate the molar mass and identify the compound. (b) To check the results from part (a), you decide to measure the molar mass based on the relative rales of effusion of the unknown gas and CO2. You find that CO2 effuses at a rate of 0.050 mol/min, whereas the unknown phosphorus fluoride effuses at a rate of 0.028 mol/min. Calculate the molar mass of the unknown gas based on these results.

Plot the data given in Table 5.3 for oxygen at 0C to obtain an accurate molar mass for O2. To do this, calculate a value of the molar mass at each of the given pressures from the ideal gas law (we will call this the apparent molar mass at this pressure). On a graph show the apparent molar mass versus the pressure and extrapolate to find the molar mass at zero pressure. Because the ideal gas law is most accurate at low pressures, this extrapolation will give an accurate value for the molar mass. What is the accurate molar mass?

Carbon dioxide, CO2, was shown lo effuse through a porous plate at the rate of 0.033 mol/min. The same quantity of an unknown gas, 0.033 moles, is found to effuse through the same porous barrier in 104 seconds. Calculate the molar mass of the unknown gas.

A 21.4-mL volume of hydrochloric acid reacts completely with a solid sample of MgCO3. The reaction is 2HCl(aq)+MgCO3(s)CO2(g)+H2O(l)+MgCl2(aq) The volume of CO2 formed is 159 mL at 23C and 731 mmHg. What is the molarity of the HCl solution?

What volume, in milliliters, of hydrogen gas at 1.33 atm and 33 C is produced by the reaction of 0.0223 g lithium metal with excess water? The other product is LiOH.

54 One way to generate oxygen is to heat potassium chlorate, KClO3. (The other product is potassium chloride.) If 386 mL of oxygen at 41 C and 97.8 kPa is generated by this reaction, what is the minimum mass of KClO3used?

105 The decomposition of mercury(II) thiocyanate produces an odd brown snake-like mass that is so unusual the process was once used in fireworks displays. There are actually several reactions that take place when the solid Hg(SCN)2 is ignited: 2Hg(SCN)2(s)2HgS(s)+CS2(s)+C3N4(s)CS2(s)+3O2(g)CO2(g)+2SO2(g)2C3N4(s)3(CN)2(g)+N2(g)HgS(s)+O2(g)Hg(l)+SO2(g) A 42.4-g sample of Hg(SCN)2 is placed into a 2.4-L vessel at 21°C. The vessel also contains air at a pressure of 758 torr. The container is sealed and the mixture is ignited, causing the reaction sequence above to occur. Once the reaction is complete, the container is cooled back to the original temperature of 21°C. (a) Without doing numerical calculations, predict whether the final pressure in the vessel will be greater than, less than, or equal to the initial pressure. Explain your answer. (b) Calculate the final pressure and compare your result with your prediction. (Assume that the mole fraction of O2 in air is 0.21.)