A 26.02 g sample of an unknown metal at 96.52 °C was placed into a coffee-cup calorimeter containing 80.0 mL of water at 19.50 °C. The final temperature of the system was found to be 21.94 °C. The density of water at 19.50 °C is 0.9983 g/mL; the specific heat of water is 4.184 J/g ·°C).

A 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.

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)?

Chlorine dioxide, ClO2, is a reddish yellow gas used in bleaching paper pulp. The average speed of a ClO2 molecule at 25C is 306 m/s. What is the kinetic energy (in joules) of a ClO2 molecule moving at this speed?