Question

Need help with the following THREE questions (22,23, & 24)

22. A 20 gram iron block at an init 8°C 20 18 ifon block at an initial temperature of 20°C is placed in 20 grams of water at an temperature of 80°C. Assuming no heat is lost to the surroundings, what would be the final temperature of the system once you reach thermal equilibrium cron = 0.449 re 449 460 cwater = 4.18 8.98J 13.6) A. 74.2°C B. 80.0°C C. 25.8°C D. 50.0°C E. 112° C por 8.48 X AT = 33.6*(60- 4T) 34.2 83.6x(60-54.2) 486. 7 434 88 23. The human eye contains a molecule called 11-cis-retinal that changes conformation when struck with light of sufficient energy. The change in conformation triggers a series of events that results in an electrical signal being sent to the brain. The minimum energy required to change the conformation of 11-cis-retinal within the eye is about 164 kJ/mol. Calculate the longest wavelength of light visible to the human eye. A. 3.20 nm B. 730 nm C. 820 nm D. 1.21 x 10-21 nm 24. Magnesium metal reacts with hydrochloric acid to produced hydrogen gas and magnesium chloride by the following balanced reaction. Mg(s) + 2HCl(aq) + MgCl2 (aq) + H2(g) When 1 mol of Me is allowed to react with excess hydrochloric acid in a constant pressure calorimeter (similar to a coffee cup calorimeter), the temperature of the solution is barved to rise from 24.50 °C to 75.96 °C. The total mass of the solution is measured to be 2.2 kg and the specific heat capacity of the solution is 4.18 J/g.c. Determ termine the enthalpy change of the reaction, AH rx, paying particular attention to the sign ATS 75.96 A -473 kJ 2,200gr color B. +473 kJ 651.46" 4.183/9.c C +0.473 kJ D. -699 kJ E +699 kJ 4. 18x2200x 51.46 = -473kſ

Answer 1

22) heat gain by iron = heat lost by water

mC_{​​​​​iron}(∆T) =mC_{​​​​​water}(∆T)

20×0.449 ×(T-20) = 20×4.18×(80-T)

T = 74.2 °c

23) E = 164×10³ /6 .022×10²³

= 2.72×10^-19 J

E = hC/wavelength

Wavelength = 6.626×10^-34×3×10⁸/2.72×10^-19

=> 730 mm

24) Heat(q) = mS(∆T)

= 2.2×1000×4.18×(75.96-24.5)

= 473 kJ

∆H = -q

= -473 kJ