Concept explainers
Classify each of the following as exothermic or endothermic:
a.
b.
c.
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CHEMISTRY: AN INTRODUCTION TO GENERAL, O
- Quinone is an important type of molecule that is involved in photosynthesis. The transport of electrons mediated by quinone in certain enzymes allows plants to take water, carbondioxide, and the energy of sunlight to create glucose. A 0.1964-g sample of quinone (C6H4O2) is burned in a bomb calorimeter with a heat capacity of 1.56 kJ/C. The temperature of the calorimeter increases by 3.2C. Calculate the energy of combustion of quinone per gram and per mole.arrow_forwardHypothetical elements A2 and B2 react according to the following equation, forming the compound AB. A2(aq)+B2(aq)2AB(aq);H=+271kJ/mol If solutions A2(aq) and B2(aq), starting at the same temperature, are mixed in a coffee-cup calorimeter, the reaction that occurs is a exothermic, and the temperature of the resulting solution rises. b endothermic, and the temperature of the resulting solution rises. c endothermic, and the temperature of the resulting solution falls. d exothermic, and the temperature of the resulting solution falls. e exothermic or endothermic, depending on the original and final temperatures.arrow_forwardAre the following processes exothermic or endothermic? a. the combustion of gasoline in a car engine b. water condensing on a cold pipe c. CO2(s) CO2(g) d. F2(g)2F(g)arrow_forward
- Classify each process as exothermic or endothermic. (a) ice melts (b) gasoline burns (c) steam condenses (d) reactants products, H = 50 kJarrow_forwardWhen calcium carbonate, CaCO3 (the major constituent of limestone and seashells), is heated, it decomposes to calcium oxide (quicklime). CaCO3(s)CaO(s)+CO2(g);H=177.9kJ How much heat is required to decompose 21.3 g of calcium carbonate?arrow_forwardInsoluble PbBr2(s) precipitates when solutions of Pb(NO3)2(aq) and NaBr(aq) are mixed. Pb(NO3)2(aq) + 2 NaBr(aq) PbBr2(s) + 2 NaNO3(aq) rH = ? To measure the enthalpy change, 200. mL. of 0.75 M Pb(NO3)2(aq) and 200. mL of 1.5 M NaBr(aq) are mixed in a coffee-cup calorimeter. The temperature of the mixture rises by 2.44 C. Calculate the enthalpy change for the precipitation of PbBr2(s), in kJ/mol. (Assume the density of the solution is 1.0 g/mL., and its specific heat capacity is 4.2 J/g K.)arrow_forward
- In a calorimetric experiment, 6.48 g of lithium hydroxide, LiOH, was dissolved in water. The temperature of the calorimeter rose from 25.00C to 36.66C. What is H for the solution process? LiOH(s)Li(aq)+OH(aq) The heat capacity of the calorimeter and its contents is 547 J/C.arrow_forwardThe temperature of the cooling water as it leaves the hot engine of an automobile is 240 F. After it passes through the radiator it has a temperature of 175 F. Calculate the amount of heat transferred from the engine to the surroundings by one gallon of water with a specific heat of 4.184 J/g oC.arrow_forwardThe standard enthalpy of formation of solid barium oxide, BaO, is 553.5 kJ/mol, and the standard enthalpy of formation of barium peroxide, BaO2, is 634.3 kJ/mol. (a) Calculate the standard enthalpy change for the following reaction. Is the reaction exothermic or endothermic? 2 BaO2(s) 2 BaO(s) + O2(g) (b) Draw an energy level diagram that shows the relationship between the enthalpy change of the decomposition of BaO2, to BaO and O2, and the enthalpies of formation of BaO2(s) and BaO2(s).arrow_forward
- Consider the substances in Table 7-1. Which substance requires the largest amount of energy to raise the temperature of 25.0 g of the substance from l5.0C to 37.0C? Calculate the energy. Which substance in Table 7-1 has the largest temperature change when 550. g of the substance absorbs 10.7 kJ of energy? Calculate the temperature change.arrow_forwardHydrogen cyanide is used in the manufacture of clear plastics such as Lucite and Plexiglas. It is prepared from ammonia and natural gas (CH4). 2NH3(g)+3O2(g)+2CH4(g)2HCN(g)+6H2O(g) The reaction evolves 469 kJ of heat per mol of HCN formed. Is the reaction endothermic or exothermic? What is the value of q when 2 mol HCN forms?arrow_forwardConsider the following reaction: CH4(g)+2O2(g)CO2(g)+2H2O(l)H=891KJ Calculate the enthalpy change for each of the following cases: a. 1.00 g methane ics burned in excess oxygen. b. 1.00 103 L methane gas at 740. torr and 25C are burned in excess oxygen. The density of CH4(g) at these conditions is 0.639 g/L.arrow_forward
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