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An unknown compound was discovered in a laboratory by a chemist. To be able to
find out the molecular formula of this compound, 1.13 g of the unknown compound was
placed into a combustion chamber, and end of the analysis 1.252 g CO2 and 0.3404 g
H2O were obtained. Later, the chemist analyzed the molar mass of the compound as 240
g/mol. What is the molecular formula of the unknown compound?
A sample of natural gas contains 8.24 moles of methane (CH4), 0.421 mole of ethane (C2H6), and 0.116 mole of propane (C3H8). If the total pressure of the gases is 1.37 atm, what are the partial pressures of the gases?
Assuming no change in temperature and pressure, Calculate the volume of O2 (in liters) required for the complete combustion of 14.9 L of butane (C4H10):
C4H10(g) + O2(g) → CO2(g) + H2O(l )
Compare the density of CO2 at 0oC and 380 torr with its density at STP.
At 10.0oC and 102.5 kPa, the density of dry air is 1.26 g/L. What is the average “molar mass” of dry air at these conditions?
In an experiment, x g of sodium is burnt completely in air. The product formed is dissolved in water to form a 50.0 cm3 solution. 10.0 cm3 of this solution required 33.50 cm3 of hydrochloric acid 0.10 mol dm-3 for complete neutralisation. What is the value of x?
To prevent the presence of air, noble gases are placed over highly reactive chemicals to act as inert “blanketing” gases. A chemical engineer places a mixture of noble gases consisting of 5.50 g of He, 15.0 g of Ne, and 35.0 g of Kr in a piston-cylinder assembly at STP. Calculate the partial pressure of each gas
What are the quantum numbers of the last electron of gallium and yttrium?
Answer the following questions by showing electron configuration (spdf notation)
(a) Which of the following is (are) paramagnetic? Zn, I, K+, O2-, Al
(b) Which of the following has the largest number of unpaired electrons: S, Cr2+, P, Rb,
Kr?
(c) Choose the paramagnetic atom or ion: Zn, Zn2+, Mn2+, Ar, Al3+.
(d) Which of the following has the smallest value of the first ionization energy: Ar, Cs, N,
Cu, Rb?
(e) List in order of increasing size: Cl- , Ar, K+, S2- , Ca2+. (Show the parameter that effects the size as orbital-electron skeckout)
Q10. In a Styrofoam cup, a 1.80 g sample of NaCl is added to 32.0 g H2O and stirred until
NaCl completely dissolves. The temperature of the solution drops from 25.4 to 23.1 °C.
(a) Is the process endothermic or exothermic?
(b) What is the heat of solution of NaCl expressed in kilojoules per mole of NaCl?
(Specific heat of water: 4.18 J/g °C)
