Concept explainers
Nitromethane (CH3NO2), sometimes used as a fuel in drag racers, burns according to the following equation. How much heat is released by burning 100.0 g of nitromethane?
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General Chemistry: Atoms First
- The 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 combustion of 1.00 mol liquid methyl alcohol (CH3OH) in excess oxygen is exothermic, giving 727 kJ of heat. (a) Write the thermochemical equation for this reaction. (b) Calculate the enthalpy change that accompanies the burning 10.0 g methanol. (c) Compare this with the amount of heat produced by 10.0 g octane, C8H18, a component of gasoline (see Exercise 5.41).arrow_forwardHow much heat is absorbed by a 44.7-g piece of leadwhen its temperature increases by 65.4°C?arrow_forward
- The standard molar enthalpy of formation of diborane, B2H6(g), cannot be determined directly because the compound cannot be prepared by the reaction of boron and hydrogen. It can be calculated from other enthalpy changes, however. The following enthalpy changes can be measured. 4 B(s) + 3 O2(g) 2 B2O3(s) rH = 2543.8 kJ/mol-rxn H2(g) + O2(g) H2O(g) rH = 241.8 kl/mol-rxn B2H6(g) + 3 O2(g) B2O3(s) + 3 H2O(g) rH = 2032.9 kJ/mol-rxn (a) Show how these equations can be added together to give the equation for the formation of B2H6(g) from B(s) and H2(g) in their standard states. Assign enthalpy changes to each reaction. (b) Calculate fH for B2H6(g). (c) Draw an energy level diagram that shows how the various enthalpies in this problem are related. (d) Is the formation of B2H6(g) from its elements exo- or endothermic?arrow_forwardThe process of dissolving ammonium nitrate, NH4NO3, in water is an endothermic process. What is the sign of q? If you were to add some ammonium nitrate to water in a flask, would you expect the flask to feel warm or cool?arrow_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_forward
- A 0.470-g sample of magnesium reacts with 200 g dilute HCl in a coffee-cup calorimeter to form MgCl2(aq) and H2(g). The temperature increases by 10.9 C as the magnesium reacts. Assume that the mixture has the same specific heat as water and a mass of 200 g. (a) Calculate the enthalpy change for the reaction. Is the process exothermic or endothermic? (b) Write the chemical equation and evaluate H.arrow_forwardSalicylic acid, C7H6O3, is one of the starting materials in the manufacture of aspirin. When 1.00 g of salicylic acid burns in a bomb calorimeter, the temperature of the bomb and water goes from 23.11C to 28.91C. The calorimeter and water absorb 21.9 kJ of heat. How much heat is given off when one mole of salicylic acid burns?arrow_forwardA 10.00-g sample of acetic acid, HC2H3O2, was burned in a bomb calorimeter in an excess of oxygen. HC2H3O2(l)+2O2(g)2CO2(g)+2H2O(l) The temperature of the calorimeter rose from 25.00C to 35.84C. If the heat capacity of the calorimeter and its contents is 13.43 kJ/C, what is the enthalpy change for the reaction?arrow_forward
- Hydrogen sulfide, H2S, is produced during decomposition of organic matter. When 0.5000 mol H2S burns to produce SO2(g) and H2O(l), 281.0 kJ of heat is released. What is this heat in kilocalories?arrow_forwardCalcium oxide (quicklime) reacts with water to produce calcium hydroxide (slaked lime). CaO(s)+H2O(l)Ca(OH)2(s);H=65.2kJ The heat released by this reaction is sufficient to ignite paper. How much heat is released when 28.6 g of calcium oxide reacts?arrow_forwardAn iron skillet weighing 1.63 kg is heated on a stove to 178C. Suppose the skillet is cooled to room temperature, 21C. How much heat energy (in joules) must be removed to affect this cooling? The specific heat of iron is 0.449 J/(gC).arrow_forward
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