The Sun supplies about 1.0 kilowatt of energy for each squaremeter of surface area (1.0 kW/m2,where a watt = 1 J/s). Plants produce the equivalent of about 0.20 g of sucrose (C12H22O11) per hour per square meter. Assuming that the sucrose is produced as follows, calculate the percentage ofsunlight used to produce sucrose.
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CHEMISTRY:CENTRAL SCI. W/MASTERINGCHEM
- The enthalpy change for the following reaction is 393.5 kJ. C(s,graphite)+O2(g)CO2(g) (a) Is energy released from or absorbed by the system in this reaction? (b) What quantities of reactants and products are assumed? (c) Predict the enthalpy change observed when 3.00 g carbon burns in an excess of oxygen.arrow_forwardWater gas, a mixture of carbon monoxide and hydrogen, is produced by treating carbon (in the form of coke or coal) with steam at high temperatures. (See Study Question 83.) C(s) + H2O(g) CO(g) + H2(g) Not all of the carbon available is converted to water gas since some is burned to provide the heat for the endothermic reaction of carbon and water. What mass of carbon must be burned (to CO2 gas) to provide the energy to convert 1.00 kg of carbon to water gas?arrow_forwardThe first step in the preparation of lead from its ore (galena, PbS) consists of roasting the ore. PbS(s)+32O2(g)SO2(g)+PbO(s) Calculate the standard enthalpy change for this reaction, using enthalpies of formation (see Appendix C).arrow_forward
- 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?arrow_forwardCalcium carbide, CaC2, is manufactured by reducing lime with carbon at high temperature. (The carbide is used in turn to make acetylene, an industrially important organic chemical.) Is the reaction endothermic or exothermic?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
- Methane, CH4, can be converted to methanol, which, like ethanol, can be used as a fuel. The energy level diagram shown here presents relationships between energies of the fuels and their oxidation products. Use the information in the diagram to answer the following questions. (The energy terms are per mol-rxn.) (a) Which fuel, methanol or methane, yields the most energy per mole when burned? (b) Which fuel yields the most energy per gram when burned? (c) What is the enthalpy change for the conversion of methane to methanol by reaction with O2(g)? (d) Each arrow on the diagram represents a chemical reaction. Write the equation for the reaction that converts methane to methanol.arrow_forwardLiquid hydrogen peroxide has been used as a propellant for rockets. Hydrogen peroxide decomposes into oxygen and water, giving off heat energy equal to 686 Btu per pound of propellant. What is this energy in joules per gram of hydrogen peroxide? (1 Btu = 252 cal; see also Table 1.4.)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_forward
- Niagara Falls has a height of 167 ft (American Falls). What is the potential energy in joules of 1.00 lb of water at the top of the falls if we take water at the bottom to have a potential energy of zero? What would be the speed of this water at the bottom of the falls if we neglect friction during the descent of the water?arrow_forwardFormic acid, HCHO2, was first discovered in ants (formica is Latin for ant). In an experiment, 5.48 g of formic add was burned at constant pressure. 2HCHO2(l)+O2(g)2CO2(g)+2H2O(l) If 30.3 kJ of heat evolved, what is H per mole of formic acid?arrow_forward
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