Exam 6: Thermochemistry

The heat of solution of ammonium chloride is 15.2 kJ/mol. If a 6.134 g sample of NH₄Cl is added to 65.0 mL of water in a calorimeter at 24.5 ^$\circ$ C, what is the minimum temperature reached by the solution (The specific heat of water = 4.18 J/g· ^$\circ$ C; the heat capacity of the calorimeter = 365. J/ ^$\circ$ C.)

The combustion of one mole of benzene, C₆H₆, in oxygen liberates 3268 kJ of heat. The products of the reaction are carbon dioxide and water. How much heat is given off when 183 g of oxygen are reacted with excess benzene

A 0.1326 g sample of magnesium was burned in an oxygen bomb calorimeter. The total heat capacity of the calorimeter plus water was 5,760 J/ ^$\circ$ C. If the temperature rise of the calorimeter with water was 0.570 ^$\circ$ C, calculate the enthalpy of combustion of magnesium.Mg(s) + 1/2O₂(g) $\rarr$ MgO(s)

Three separate 3.5g blocks of Al, Cu, and Fe at 25 ^$\circ$ C each absorb 0.505 kJ of heat. Which block reaches the highest temperature The specific heats of Al, Cu, and Fe are 0.900 J/g· ^$\circ$ C, 0.385J/g· ^$\circ$ C, and 0.444 J/g· ^$\circ$ C, respectively.

The reaction that represents the standard enthalpy of formation for benzene (C₆H₆) is:

A gas is allowed to expand, at constant temperature, from a volume of 1.0 L to 10.1 L against an external pressure of 0.50 atm. If the gas absorbs 250 J of heat from the surroundings, what are the values of q, w, and $\Delta$ E $~~~~~~~~~~~~~~\underline{q}~~~~~~~~~~~~~~\underline{w}~~~~~~~~~~~~~~\underline{\Delta{E}}$ A. $~~~\quad 250 \mathrm{~J} \quad-460 \mathrm{~J} \quad-210 \mathrm{~J}$ B. $\quad-250 \mathrm{~J} \quad-460 \mathrm{~J}~~~~-710 \mathrm{~J}$ C. $~~~\quad250 \mathrm{~J} \quad~~~~~ 460 \mathrm{~J} ~~~~~\quad 710 \mathrm{~J}$ D. $\quad-250 \mathrm{~J} \quad~~~~ 460 \mathrm{~J} ~~~~~~\quad 210 \mathrm{~J}$ E. $~~~\quad 250 \mathrm{~J} \quad-4.55 \mathrm{~J} \quad~~~~ 245 \mathrm{~J}$

When 18.5 g of HgO(s) is decomposed to form Hg(l) and O₂(g), 7.75 kJ of heat is absorbed at standard-state conditions. What is the standard enthalpy of formation ( $\Delta$ H ^$\circ$ _f) of HgO(s)

Which of the following processes is endothermic

What would be the standard enthalpy change for the reaction of 1.00 mole of H₂(g) with 1.00 mole of Cl₂(g) to produce 2.00 moles of HCl(g) at standard state conditions [ $\Delta$ H ^$\circ$ _f (HCl(g))= -92.3 kJ/mol)]

The residential rate for natural gas is about $15 per thousand cubic foot. Burning one cubic foot of natural gas releases about 1080 kJ of heat. How much would it cost to heat the water in a 25,000 gallon swimming pool from 52 ^$\circ$ F to 78 ^$\circ$ F, assuming all of the heat from burning the natural gas went towards warming the water (1 gal = 3.785 L; the specific heat of water = 4.184 J/g· ^$\circ$ C)

Solid sodium peroxide (Na₂O₂) reacts with liquid water yielding aqueous sodium hydroxide and oxygen gas. How much heat is released when 250.0 L of oxygen gas is produced from the reaction of sodium peroxide and water if the reaction is carried out in an open container at 1.000 atm pressure and 25 ^$\circ$ C (Given: $\Delta$ H ^$\circ$ _f[Na₂O₂(s)] = -510.9 kJ/mol; $\Delta$ H ^$\circ$ _f[NaOH(aq)] = -469.2 kJ/mol; $\Delta$ H ^$\circ$ _f[H₂O(l)] = -285.8 kJ/mol)

Which of the following processes is endothermic, given the following: S(s) + O₂(g) $\rarr$ SO₂(g) $\Delta$ H = -299 kJ/mol S(s) + 3/2 O₂(g) $\rarr$ SO₃(g) $\Delta$ H = -395 kJ/mol

A 0.1946 g piece of magnesium metal is burned in a constant-volume calorimeter that has a heat capacity of 1349 J/ ^$\circ$ C. The calorimeter contains 500. g of water and the temperature rise is 1.40 ^$\circ$ C. Calculate the heat of combustion of magnesium metal in kJ/g, given that the specific heat of water = 4.184 J/g· ^$\circ$ C.

The heat of solution of NH₄NO₃ is 26.2 kJ/mol. Heat is evolved when a solution of NH₄NO₃ is diluted by addition of more water.

The specific heats of water and iron are 4.184 and 0.444 J/g ^$\circ$ C, respectively. When equal masses of water and iron both absorb the same amount of heat, the temperature increase of the water will be 2.42 times greater than that of the iron.

Pentaborane B₅H₉(s) burns vigorously in O₂ to give B₂O₃(s) and H₂O(l). Calculate $\Delta$ H_rxn for the combustion of 5.00 mol of B₅H₉. $\Delta$ H ^$\circ$ _f[B₂O₃(s)] = -1,273.5 kJ/mol $\Delta$ H ^$\circ$ _f[B₅H₉(s)] = 73.2 kJ/mol $\Delta$ H ^$\circ$ _f[H₂O(l)] = -285.8 kJ/mol

Given H₂(g) + (1/2)O₂(g) $\rarr$ H₂O(l), $\Delta$ H ^$\circ$ = -286 kJ/mol, determine the standard enthalpy change for the reaction 2H₂O(l) $\rarr$ 2H₂(g) + O₂(g).

A feverish student weighing 75 kilograms was immersed in 400. kg of water at 4.0 ^$\circ$ C to try to reduce the fever. The student's body temperature dropped from 40.0 ^$\circ$ C to 37.0 ^$\circ$ C. Assuming the specific heat of the student to be 3.77 J/g· ^$\circ$ C, what was the final temperature of the water

Calculate the standard enthalpy change for the reaction 4A + 2B $\rarr$ 2AB + A₂ Given: 2+\rightarrow \Delta=-25.0/ 2\rightarrow2+ \Delta=35.0/

Glycine, C₂H₅O₂N, is important for biological energy. The combustion reaction of glycine is given by the equation 4C₂H₅O₂N(s) + 9O₂(g) $\rarr$ 8CO₂(g) + 10H₂O(l) + 2N₂(g) $\Delta$ H ^$\circ$ _rxn = -3857 kJ/mol Given that $\Delta$ H ^$\circ$ _f[CO₂(g)] = -393.5 kJ/mol and $\Delta$ H ^$\circ$ _f[H₂O(l)] = -285.8 kJ/mol, calculate the enthalpy of formation of glycine.