25.0 g of water at 15.0 DegreeC are combined with 350. g of water at 75.0 Degree

Question

25.0 g of water at 15.0 DegreeC are combined with 350. g of water at 75.0 DegreeC. Calculate the final temperature reached, assuming no heat loss or gain from the surroundings. A coffee-cup calorimeter contains 150.0 ml. of 0.725 M HCl at 22.4 DegreeC. When 2.50 g of Fe metal is added to the acid, it causes the temperature of the solution to increase to 31.6 DegreeC. 2Fe(s). 6HCl(aq) rightarrow 2FeCl_3(aq) + 3H_2(g) AH_nm = ? What is the value of DeltaH_nm of the reaction? Assume the density and specific heat of the solution is the same as that of pure water. A bomb calorimeter has a heat capacity of 2.47 kJ/DegreeC. When a 0.105-g sample of ethylene (C_2H_4) was burned in this calorimeter, the temperature increased by 2.14 DegreeC. Calculate the energy of combustion for one mole of ethylene. Use the following data to calculate the standard heat (enthalpy) of the following reaction: C_2H_4(g) + H_2(g). C_2H_6(g) An important step in the synthesis of nitric acid is the conversion of ammonia to nitric oxide. 4NH_3(g) + 5O_2(g) rightarrow 4NO(g) + 6H_2O(g) Calculate DeltaH_m times n^o for this reaction.

Explanation / Answer

Answer to question 6.

You know that the energy release from one object is absorbed by another object (when both from different temperature are in touch).

Q = -Q (one positive because absorbs energy and the other negative because releases energy).

Now, knowking that Q is calculated by mass x heat capacity x change in temperature (T final - T initial) we can re - write the equation like

m1 C (Tf - Ti1) = - m2 C (Tf - Ti2) where 1 would be the mass and temperature of the 25 grams of water at 15 °C and 2 is for the 350 g of water at 75 °C. Also knowing that C = 1 cal/g °C

(25 g)(1 cal/g °C)(Tf - 15 °C) = - (350 g)(1 cal / g °C)(Tf - 75 °C)

Doing the math we have that 25 Tf - 373 = -350 Tf + 26250

375 Tf = 26625
Tf = 71 °C.

For the other problems you need a physicochemistry book with the tables of standart enthalpies of formation. To calculate the enthalpy of a reaction you need to substract the sum of enthalpies of reactants to the sum of enthalpies of products Eproducts - Ereactants.
Dont forget to balance the reaction!!

Try posting just one question at the time!
Good luck

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