ong Ne and water Vapor. IThe total volumé iS 635.0 ml at 25.0 C. The atmospheric
ID: 568324 • Letter: O
Question
ong Ne and water Vapor. IThe total volumé iS 635.0 ml at 25.0 C. The atmospheric pressure is 67.7 cm and the vapor pressure of water at 25.0 °C is 23.8 torr The Ne is removed and placed into another 1.35 L. container. The Ne exerts a pressure of 155 mm Hg at 25.0°C. (The molar mass of MgCO, is 84.31) MgCO3 (s) MgO(s) + CO2 (g) Calculate the MgCO2 in the mixture. 2) A student received a mixture containing KC/KCIO3 and MnO2. She analyzed the sample and obtained the following data. the following data: Weight of test tube and contents before heating Weight of test tube after heating Weight of test tube Volume of water displaced Barometric reading Oxygen temperature Vapor pressure of water 61.88 g 60.70 g 34.38 g 1445.0 mls 75.21 cm Hg 25.3°C 31 torr 2KCIO3 2 KCl + 302 Calculate the percent KCIO, in the mixture using the above volume of oxygen data 3) Calculate the total heat change when 100.0 g of ice water at-20 was heated to steam water at 120,00C Heat of vaporization of water AH vap 2.260 J/gExplanation / Answer
weight in the testtube after heating (exclusive of the weight of the testtube) = (61.88-34.38)-(60.70-34.38) g =27.5 - 26.32 gm. = 1.18 gm.
This is the weight of the O2 leavin the container.
1.18 gm O2 = 0.07 moles
pressure = 75.21 cm of Hg = 75.21/76 atm= 0.98 atm.
The most important thing to notice here is that the pressure at which the gas is collected includes the water vapor as well, so in order to get the proper pressure for the oxygen you must eliminate the water vapor. Vapour pressure of water is 31 torr = 0.040 atm.
according to the ideal gas law PV = nRT
V = nRT/P
= n * 0.082 * 298.3/(0.98 -0.040)= 0.07* 24.95 L.= 1.821 L.
According to the reaction
3* 16 gm of O2 is found from 2 * 122.55 = 245.1 gm of KCLO3.
Thus 1.821 gm yeilded 9.298 gm KCLO3.
THe mass of he KCLO3 + KCL +MnO2 is the mass of the test tube after O2 has escaped .
Thus the mass is 60.70 gm - 34.38 gm(mass of the empty test tube) = 26.32 gm .
% of KCLO3 = 35.32 % of KCLO3.
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