FALL 201 CHEM 1711&1811 Hydrogen peroxide, H,O, is used as an antiseptic. It can
ID: 548904 • Letter: F
Question
FALL 201 CHEM 1711&1811 Hydrogen peroxide, H,O, is used as an antiseptic. It can be prepared change is H2 (g) 2. in a prsing the data + o, (g) Hao, (l). Calculate the enthalpy change for this using the data below. }--572 kJ 2H2 (g) + 02 (g) 2H20 (I) ; kJ . A sample of pure ideal gas in a 2.00 L flask exerts a pressure of 223 torr at 15 C. The gas weighs 848 mg. What is its molar mass in grams/mol? g/mol a certain sample of hydrogen gas, the average speed of the molecules is 1248 m/s. lculate the temperature of this sample in degrees Celsius. oCExplanation / Answer
invert rxn 1 and divide by 2
H2O + 1/2O2 = H2O2 H1 = (-196)(-1/2) = 98
divide rxn 2 by 2
H2 + 1/2O2 = H2O H2 = -572/2 = -286
add both reactions
H2 + 1/2O2 +H2O + 1/2O2 = H2O2+ H2O H1 =98-286 = -188
cancel commont erms
H2 + O2 = H2O2 H =-188 kJ
Q3
MM = mass/mol
PV = nRT
n = PV/(RT) = (223)*2/(62.4*(15+273))
n = 0.02481
MM = (0.848/0.02481) = 34.18 g/mol
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