tutorial 1 DAS12203

Tutorial 1

1.	(a)	Calculate the volume that 0.80 g methane, CH4 occupies at 52 °C and 100 kPa. (RAM: H, C, R)
	(b)	Zinc metal react with hydrochloric acid to produce hydrogen gas, H2. Zn (s)  +  HCl (aq)   à   ZnCl2 (aq)   +   H2 (g) The volume of H2 collected over water at 23 °C is 260 ml and the total pressure is 740 mmHg. (Water vapour pressure at 23 °C is 21.1 mmHg). (i)                 What is the partial pressure of H2? (ii)               How many milligrams of H2 were collected? (RAM: H, Cl, Zn, R)
2.	(a)	The first step in industrial recovery of zinc from th zinc sulphide ore is roasting: 2ZnS (s)  +  3O2 (g)   à  2ZnO (s)   +   2SO2 (g)   ∆H = -879 kJ/mol (i)                 Skecth an enthalpy diagram of the process. (ii)               Calculate the heat evolved (in kJ) per gram of ZnS roasted. (RAM: Zn, S)
3.	(a)	Consider the reaction  A à  B. The rate of the reaction is 1.6x10-2 Ms-1 when the concentration of A is 0.35 M. Calculate the rate constant, k if the reaction is (i)                 First order in A (ii)               Second order in A
		(i)
	(b)	(ii)     Define the half-life of a reaction. (iii)   Write the equation relating the half life of a first order of reaction to the rate constant, k. (iv)   Determine the half life of a compound if 75 % of a given sample of the compound decomposes in 60 min. Assume first order kinetics.
	(c)	The rate constant for a second order reaction 2NO2 (g)  à  2NO (g)  +  O2 (g) is 0.54 M-1s-1 at 300 °C. How long (in second) would it take for the concentration of NO2 to decrease from 0.562 M to 0.128 M.
4	(a)	Adenosine triphosphate (ATP) contain 10 carbon, 11 hydrogen, 13 oxygen, 5 nitrogen and 3 phosphorous atoms per molecule. (i)                 Write the molecular formula of ATP. (ii)               What is the number of ATP molecules in 10.0 g of ATP? (RAM: H, C, N, O, P, NA)
5.	(a)	Draw the lewis structure of ammonium ion, NH4+ and determine the formal chargefor each atom in the ion. (Atomic no., Z: N, H)
	(b)	(i) Which of the following are exceptions to the Lewis octet rule? BeF2 or SO3 (ii) Use forma charge to prove that the structure you choose in (i) is stable (Atomic no.,Z: Be=, O=, F=, S=,)
	(c)	Draw Lewis structure and the resonance forms of NO2F (N is cetral atom). (atomic no., Z: N=, O=, F=,)
6.	(a)	What is the molar mass of a gas that has density of 575 g/L at STP? (R =    )
	(b)	Boron hydride, B4H10­ reacts with oxygen to produce B2O3 and H2O 2B4H10 (s)   +   11O2(g)   à   4B2O3 (s)   +   10H2O (g) If 0.05 g B4H10 reacts with excess O2 (i)                 Write the stoichiometric relationship between B4H10­ and H2O (ii)               Find the number moles of B4H10­ and H2O (iii)             What is the pressure of the gaseous H2O in 425 L flask at 30 °C? (RAM: H, B, O, R = )
7.	(a)	A 100.0 g copper sample at 100 °C is added to 50.0 g of water at 26.5 °C. Determine the final temperature of the copper – water mixture. (SCu = 0.385 J.g-1.°C-1, Swater = 4.184 J.g-1°C-1)
	(b)	Calculate ∆H for the reaction N2H4 (l)  +  2H2O (l)  à  N2 (g)  +  4H2O (l) Given the following set of reaction N2H4 (l)  +  O2  à  N2 (g)  +  2H2O (l)                  ∆H = -622.2kJ H2 (g)  +  1/2O2 (g)  à  H2O (l)                             ∆H = -285.8 kJ H2 (g)  +  O2 (g)  à  H2O2 (l)                                 ∆H = -187.8 kJ