CH4 (g)  + 2 O2 (g)  -->  CO2 (g) + 2H2O (g)       Δ H = -882 kJ/mol   Using the equation above, how many grams of water will form if 655 kJ of energy was released.

Compounds with carboncarbon double bonds, such as ethylene, C2H4, add hydrogen in a reaction called hydrogenation. C2H4(g)+H2(g)C2H6(g) Calculate the enthalpy change for this reaction, using the following combustion data: C2H4(g)+3O2(g)2CO2(g)+2H2O(l);H=1411kJC2H6(g)+72O2(g)2CO2(g)+3H2O(l);H=1560kJH2(g)+12O2(g)H2O(l);H=286kJ

What 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.

If a reaction produces 1.506 kJ of heat, which is trapped in 30.0 g of water initially at 26.5 °C in a calorimeter like that in Figure 5.12, what is the resulting temperature of the water?

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.

What quantity of heat energy must have en applied to a block of aluminum weighing 42.7 g if the temperature of the block of aluminum increased by 15.2 °C? (See Table 10.1.)

We 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.

Hydrazine, N2H4, is a colorless liquid used as a rocket fuel. What is the enthalpy change for the process in which hydrazine is formed from its elements? N2(g)+2H2(g)N2H4(l) Use the following reactions and enthalpy changes: N2H4(l)+O2(g)N2(g)+2H2O(l);H=622.2kJH2(g)+12O2(g)H2O(l);H=285.8kJ

Enthalpy a A 100.-g sample of water is placed in an insulated container and allowed to come to room temperature at 21C. To heat the water sample to 41C, how much heat must you add to it? b Consider the hypothetical reaction,2X(aq)+Y(l)X2Y(aq)being run in an insulated container that contains 100. g of solution. If the temperature of the solution changes from 21C to 31C, how much heat does the chemical reaction produce? How does this answer compare with that in part a? (You can assume that this solution is so dilute that it has the same heat capacity as pure water.) c If you wanted the temperature of 100. g of this solution to increase from 21C to 51C, how much heat would you have to add to it? (Try to answer this question without using a formula.) d If you had added 0.02 mol of X and 0.01 mol of Y to form the solution in part b, how many moles of X and Y would you need to bring about the temperature change described in part c. e Judging on the basis of your answers so far, what is the enthalpy of the reaction 2X(aq) + Y(l) X2Y(aq)?

Which of the enthalpies of combustion in Table 5.2 the table are also standard enthalpies of formation?