Question

3. Air bags deployed in car accidents use a series of reactions to rapidly generate nitrogen gas in order to inflate the airbag. The first reaction is the decomposition of sodium azide (NaN,) to form nitrogen gas and solid sodium metal. The sodium metal then reacts with solid potassium nitrate to form more nitrogen gas, as well as sodium oxide and potassium oxide (both as a solid). A. Write and balance the reactions described above (including correct state for each compound) B. If an average airbag has a volume of 20.0 L, how many moles of nitrogen gas are needed to produce a pressure of 1645 torr at 25.0°C? C. Taking into account that both reactions produce nitrogen gas, how many grams of sodium azide and potassium nitrate are required to produce the required moles (from Part B.) D. Using the enthalpies of formation provided here and in your textbook, calculate AHR for both reactions above. Then, calculate the amount of energy released or absorbed during the reactions, using the mass of reactants from C. AH' (KJ/mol) 21.3 Compound NaN_(s) Na, O(S) KNO3(S) K 0(s) -414.2 -494.6 -361.5

Answer 1

09082298 A. The balanced reactions are Na Ng(s) - 2 Na(s) + 3 Ng() 0 LON(S) + 2 KNO3 (5) K2015)+ 5 NaZO(S) + N2 (3) - B. We have the relation w ith - PV = nRT vdex 381 Here, v= 20t, P= 1645 torr = 1445/460 alin. lin = 2.164 alin R = 0.082 t atinstind, T = 273 + 25 = 2988, n. using the alcove relation, na enota 8-1648 2098 = 1** mol C. Multiplying by 57 10 NaN3 (3) 10 Na(s) + 15 N2 (8) Now 2 + » 10 Na N3 (5) + 2 K NOG() -- K2018) + 5 Nago(s) + 16 NZ (9) ► Maksi 10ml 22 mol mol 5 mol 16 mol from the above reaction, 16 mol of Na produced from NaNo = 10 and ukomis 177 2 0x1 +7 mel = 1.11.11 from the all are reaction, alles 10 me of NaNz requires KN z = 2 mol - - 3X1 0-222mol Amount of NaNg required a number of moles molecular weight - 1'11x 65 g = 72 15 g amount of knoy required 2 0 222X LOI! 9-21449

2. For reaction 6 ) Ahown 2 24H f (Na) + 34 Hof (N) - 24H f (Nang) 20 + 0 - (23 213) -- 42'6 kJXMCA For reaction - Ahoren & AHf (R20) + 5AHA (NO) + A Hq (N2) - 1044f (Na) - 24H f ( KNO3) 2-361'5+5*(-4142) +0 -0-2*(-494'6) = - 1443.3 kJ Enno to get the combined reaccion & a rallies 0x5 + 2 => 10 NAN3(S) + 2KNO3(S) —— X20(s) + 5 Na, 0(s) + 16N2 (9) H = 5* 4H7m(1) + 4Hoxn (2) = 5x(-426) -4443'3 kJ) miel -- 1656°3 ku Therefore, 10 ул | b JoN, Atleos МАЯ 2 6 S6 3 3 1 " " - 16563 x111 KJ similarly, 0222 mol of KNOB releases energy 183 85 ks und ta 183.84 kJ Therefore, energy released during the reactions is 183.85 KJ , 10