Chemistry 1A Exam #3 Sample Questions 1. Methanol is the fuel in \"canned heat\"

Question

Chemistry 1A Exam #3 Sample Questions 1. Methanol is the fuel in "canned heat" containers (eg, Sterno) that are used to heat foodsat Sterno) that are used to heat foods at cocktail parties. The combustion of methanol follows the thermochemical equation: How many kilojoules are liberated by the combustion of 77.0 g of methanol? 2. A 35.0 g piec of mnum (which has a meler heat capacity of 24.03 JimolC) is heated to 92.4 Cand heat capacity of 24.03 J/mol C) is heated to 92.4°C and dropped into a coffee cup calorimeter containing water (specific heat capacity of water is 4.184 Ji/g C) initially at 20.3°C. The calorimeter. final temperature of the water is 24.9 Calculate the mass of water in the 3. Use the following equations: AH--622.2 MI-285.6J Using Hess's Law, cakculate the enthalpy change for the reaction: Nhld) + 2H0(1) NAO + 411,0(1) 4 Which one of the following statements is false? a. The change in internal energy, AE, for a process is equal to the amount of heat absorbed/released at constant volume, q. b. b. The change in cnthalpy, Al, for a process s qual to the amount of heat absorbed/relessed a The change in enthalpy, /l, for a cess is equal to the amount of heat constant pressure, q c. A bomb calorimeter measures AH directly d. Ifa, for a process is negative, the process is exothermic. e. The freezing of water is an example of an exothermic reaction. Thefrequency of infrared light is 3.50 x 1014 what is the energy of a single photon of this light and of mole of such photons? 0 x 10 Hz What is the energy of a single photon of this light and 6 Calculate the wavelength of the line in the Lyman series that results from the transition n-3 tom- 7. What type of orbital is designated -2,1-2, m-+1? a. 4s b. 4p d. 2f none 8. For the quantum numbers n -5,1-3, what are the possible values for m?

Explanation / Answer

1. 2CH3OH + 3O2 ----> 2CO2+ 4H2O DH = -1199 kj

No of moles of CH3OH = 77/32 = 2.4 mole

2 mole CH3OH = 1199 KJ

2.4 mole CH3OH   = 1199*2.4/2 = 1438.8 Kj

HEAT RELEASED = 1438.8

2.

Qlost by metal   = q gained by water

(35/27)*24.03*(92.4-24.9)   = mwater*4.184*( 24.9-20.3)

mwater   = 2102.6 / 19.24 = 109.3 grams

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