I need help with these same or exam questions. I feel like I was going the right

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I need help with these same or exam questions. I feel like I was going the right direction, but my answers don't seem right. I would like to see them done out to see if my equations are correct 6-52 Chvemistry 1 Predict some common process to be exothermic ot endothermic and determine their sign of 1i. Apply AHp in thermochemical stoichiometric calculations. Calcalate Al nbso caloey dat. 3. Sample Exam Questions Predict if the following processes are exo-or endothermic. Rationalize sign for 11. A) B) C) 1. Condensation of water steam. Combustion of wood. Nuclear fusion in the Sun. 2. Two solutions were both at 20.0 °C initially. When they are mixed, the temperature of the solution became 18.0 °C. Is the reaction between the two solutions endo- or exothermic? What is the sign of its AH n? Briefly support your conclusion. An unknown metal is either aluminum, iron or lead. If 150. g of this metal at 150.0 °C was placed ina calorineter that contains 200. g of water at 25.0 and the final temperature was found to be 34.3 °C after thermal equilibrium was achieved. Assume heat was only transferred between water and metal, what is the identify of this metal? Some specific heat values of metals and water given below may be 3. useful. Specific heats, J/g C) Fe (0.449) Pb (0.128) A (0.903) H2O (4.184) H2A and BOH are acid and base and they react according to the following balanced equation: 4. If 0.20 moles of BOH reacted with excess amount of H2A solution and 1500. J of heat was released by the reaction, what is the H'm for the reaction as written above? l, is one substance that can be used in cold pack. If 5. NH4NOs, whose heat of solution is 25.7 kJ/mo the goal is to decrease the temperature from 25.0 °C to 5.0 °C, how many grams of NH4NOs should we use for every 100.0 g of water in the cold pack? Assume no heat was lost outside of cold pack, and the specific heat of the resulted solution was the same as water, or 4.184 J/(g C) Notr: Heat of solution for a speifhe swbstance is the beat involbed uben disolsing this ubstance in wuter to make a solution

Explanation / Answer

1. A) condensation of water = Exothermicprocess ( DH = -ve)

   b) combustion of wood = exothermic ( DH = -ve)

   c) Nuclear fusion in sun = exothermic ( DH = -ve)

2. As temperatureof mixer decreases. it is endothermic process exothermic ( DH = +ve)

3.

heat lost by metal = heat gained by water

m*s*DT = mwater*swater*DT

150*s*(150-34.3) = 200*4.184*(34.3-25)

S = specific heat of metal = 0.448 j/g.c

which is closer to Fe metal

the meatl is Iron.

4. H2A + BOH -----> B2A + 2H2O

nO OF MOLES OF BOH reacted = 0.2 mole

amount of energy released = 1500 j

so that

DH rxn = 1500*2/0.2 = 15000 j

       = 15 kj/mol

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