General chem I question?
Solve the following problems. a) How many moles of gas are contained in 890.0 mL at 21.0 °C and 750.0 mm Hg pressure? b) What volume will 1.27 moles of helium gas occupy at STP? c) At what temperature will 0.654 moles of neon gas occupy 12.30 liters at 1.95 atmospheres?
Answer:
For each part, use PV = nRT (with R=8.314 J/mol/K) as the main formula, and be sure to have correct units for your different variables.
a)
First, let's convert to friendlier units...
750 mmHg = 10^5 Pa
21 C = 294.15 K
890 mL = .00089 m^3
n =PV/RT = 100000*0.00089 / (8.314*294.15)
n=0.0364 mol
b)
At STP, we have T = 0C = 273.15K and P = 1atm = 101325 Pa
V = nRT/P = 1.27*8.314*273.15/101325
V = 0.0285 m^3 = 28.5 L
c)
12.30L = 0.0123 m^3
1.95 atm = 197583.75 Pa
T = PV/nR = 197583.75*0.0123 / (0.654*8.314)
T = 446.96 K (can be rounded to 447K)
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