Concept explainers
(a)
Interpretation:
The balanced chemical equation for the formation of
Concept introduction:
The enthalpy of reaction can be calculated using the following relation.
Here,
(b)
Interpretation:
The balanced chemical equation for the formation of
Concept introduction:
The enthalpy of reaction can be calculated using the following relation.
Here,
(c)
Interpretation:
The balanced chemical equation for the formation of
Concept introduction:
The enthalpy of reaction can be calculated using the following relation.
Here,
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General Chemistry: Principles and Modern Applications (11th Edition)
- When lightning strikes, the energy can force atmospheric nitrogen and oxygen to react to make NO: N2(g)+O2(g)2NO(g)H=+181.8kJ (a) Is this reaction endothermic or exothermic? (b) What quantities of reactants and products are assumed if H = +181.8 kJ? (c) What is the enthalpy change when 3.50 g nitrogen is reacted with excess O2(g)?arrow_forwardThe equation for the fermentation of glucose to alcohol and carbon dioxide is: C6H12O6(aq) 2C2H5OH(aq) + 2CO2(g) The enthalpy change for the reaction is 67 kJ. Is this reaction exothermic or endothermic? Is energy, in the form of heat, absorbed or evolved as the reaction occurs?arrow_forwardWhat mass of acetylene, C2H2(g), must be burned to produce 3420 kJ of heat, given that its enthalpy of combustion is 1301 kJ/mol? Compare this with the answer to Exercise 5.91 and determine which substance produces more heat per gram.arrow_forward
- The thermochemical equation for the burning of methane, the main component of natural gas, is CH4(g)+2O2(g)CO2(g)+2H2O(l)H=890kJ (a) Is this reaction endothermic or exothermic? (b) What quantities of reactants and products are assumed if H = 890 kJ? (c) What is the enthalpy change when 1.00 g methane burns in an excess of oxygen?arrow_forwardA 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_forwardA 50-mL solution of a dilute AgNO3 solution is added to 100 mL of a base solution in a coffee-cup calorimeter. As Ag2O(s) precipitates, the temperature of the solution increases from 23.78 C to 25.19 C. Assuming that the mixture has the same specific heat as water and a mass of 150 g, calculate the heat q. Is the precipitation reaction exothermic or endothermic?arrow_forward
- A 21.3-mL sample of 0.977 M NaOH is mixed with 29.5 mL of 0.918 M HCl in a coffee-cup calorimeter (see Section 6.6 of your text for a description of a coffee-cup calorimeter). The enthalpy of the reaction, written with the lowest whole-number coefficients, is 55.8 kJ. Both solutions are at 19.6C prior to mixing and reacting. What is the final temperature of the reaction mixture? When solving this problem, assume that no heat is lost from the calorimeter to the surroundings, the density of all solutions is 1.00 g/mL, the specific heat of all solutions is the same as that of water, and volumes are additive.arrow_forwardA 29.1-mL sample of 1.05 M KOH is mixed with 20.9 mL of 1.07 M HBr in a coffee-cup calorimeter (see Section 6.6 of your text for a description of a coffee-cup calorimeter). The enthalpy of the reaction, written with the lowest whole-number coefficients, is 55.8 kJ. Both solutions are at 21.8C prior to mixing and reacting. What is the final temperature of the reaction mixture? When solving this problem, assume that no heat is lost from the calorimeter to the surroundings, the density of all solutions is 1.00 g/mL, and volumes are additive.arrow_forwardWe burn 3.47 g lithium in excess oxygen at constant atmospheric pressure to form Li2O. Then, we bring the reaction mixture back to 25 C. In this process 146 kJ of heat is given off. Calculate the standard formation enthalpy of Li2O.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_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_forwardA rebreathing gas mask contains potassium superoxide, KO2, which reacts with moisture in the breath to give oxygen. 4KO2(s)+2H2O(l)4KOH(s)+3O2(g) Estimate the grams of potassium superoxide required to supply a persons oxygen needs for one hour. Assume a person requires 1.00 102 kcal of energy for this time period. Further assume that this energy can be equated to the heat of combustion of a quantity of glucose, C6H12O6, to CO2(g) and H2O(l). From the amount of glucose required to give 1.00 102 kcal of heat, calculate the amount of oxygen consumed and hence the amount of KO2 required. The ff0 for glucose(s) is 1273 kJ/mol.arrow_forward
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