Question

Question 1 (3 marks) A concrete highway is built of slabs 12 m long (at 15°C). How wide should the expansion cracks be- tween the slabs be at 15°C to prevent buckling of the concrete over the range of temperature -30°C to +50°C? The coefficient of thermal expansion for concrete is 12 x 10""(Cº). Question 2 (3+3 = 6 marks) (a) At 18.0°C, a certain quantity of oxygen occupies a volume of 61.5 L at an absolute pressure of 2.45 atm. What is the mass of the oxygen? The molecular mass of the oxygen molecule is 32.0 u. (b) The oxygen is now compressed to 48.8 L and at the same time the temperature is raised to 56.0°C. What will the new pressure be? Question 3 (4 marks) When a 290 g piece of iron at 180°C is placed in a 95 g aluminium calorimeter cup containing 250 g of glycerin at 10°C, the final temperature is observed to be 38°C. Estimate the specific heat capacity of glycerin. The specific heat capacity for iron is 450 J/(kg.K) and for aluminium is 900 J/(kg.K).

Answer 1

Answer 1:

Anunt Expension between 15 and soc. DL= LLOOT - (12.6166) ( 12) (85°C) = 1448106 x 35 = 5040 X 106 0.504 cm

Answer 2

:

of T-186-2916 -61.5L = 61.5 MP3 P 2:45 atm = 2.95 Xc/3XDP4 PV-NRT; M32710 kq. letll be in leg of Or. Puwet - m PVM = 6.45 XP013X100 (615X) (32436) 8319x 291. XID -0.2019kq - 2018 | T2=51c =329 le. Ve=988L Cowevne noef moles, REMER (0) / 829) 295 aten -3491 atm

Answer 3:

The expression for the hear lost by the iron is, Q- 71-T) Here, w is mass of iron, is the specific heat capacity of iron, T... is initial tetuperature of irou, 7 is the final retuperature. , and 38 C Substitute 0.290 kg forw. : 450 kgc forca 180C for for T. 9 = 7 12-) = (0.290 ks) 450 Jkz C)180°C-38°C) - 18331 The total heat gained by the aluminum and the glycerin is, Q=MfxT-T+FT-TA

Here, w is mass of aluminum cup. C is the specific heat capacity of aluminum, Twis initial temperature of aluminum, T is the final temperature, is mass of glycerin, is specific heat capacity of glycerin, and is initial tenperature of glycerin, Hence, the heat gained by the aluminum and the glycerin is, 9. = (0.095 kg) 900 J kg-C(38°C-10°C) +(0.095 kg), 38C-10C) = 2394 J+0.250 kg, (28C) The heat lost by the iron is equal to the heat gained by the aluminium and the glycerin is, 23945 -0.095 kg 28°C) =18531 -18531J-2394 0.250 ks (250) -2.3x10'J Therefore, the specific heat capacity of glycerin is 23x10'J.