Another reaction that is used to propel rockets is N2O4(l)+2N2H4(l)3N2(g)+4H2O(g) This reaction has the advantage that neither product is toxic, so no dangerous pollution is released. When the reaction consumes 10.0 g liquid N2O4, it releases 124 kJ of heat. (a) Is the sign of the enthalpy change positive or negative? (b) What is the value of H for the chemical equation if it is understood to be written in molar quantities?

Explain the difference between heat capacity and specific heat of a substance.

Which of the following substances have an enthalpy of formation equal to zero? a. Cl2(g) b. H2(g) c. N2(l) d. Cl(g)

Ethylene glycol, HOCH2CH2OH, is used as antifreeze. It is produced from ethylene oxide, C2H4O, by the reaction C2H4O(g)+H2O(l)HOCH2CH2OH(l) Use Hesss law to obtain the enthalpy change for this reaction from the following enthalpy changes: 2C2H4O(g)+5O2(g)4CO2(g)+4H2O(l);H=2612.2kJHOCH2CH2OH(l)+52O2(g)2CO2(g)+3H2O(l);H=1189.8kJ

Alloys When a 58.8-g piece of hot alloy is placed in125 g of cold water in a calorimeter, the temperature ofthe alloy decreases by 106.1°C, while the temperature ofthe water increases by 10.5°C. What is the specific heat ofthe alloy?

Hydrogen sulfide, H2S, is a poisonous gas with the odor of rotten eggs. The reaction for the formation of H2S from the elements is H2(g)+18S3(rhombic)H2S(g) Use Hesss law to obtain the enthalpy change for this reaction from the following enthalpy changes: H2S(g)+32O2(g)H2O(g)+SO2(g);H=518kJH2(g)+12O2(g)H2O(g);H=242kJ18S8(rhombic)+O2(g)SO2(g);H=297kJ

A 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?

You wish to heat water to make coffee. How much heat (in joules) must be used to raise the temperature of 0.180 kg of tap water (enough for one cup of coffee) from 30C to 96C (near the ideal brewing temperature)? Assume the specific heat is that of pure water, 4.18 J/(gC).

A typical fat in the body is glyceryl trioleate, C57H104O6. When it is metabolized in the body, it combines with oxygen to produce carbon dioxide, water, and 3.022104 kJ of heat per mole of fat. (a) Write a balanced thermochemical equation for the metabolism of fat. (b) How many kilojoules of energy must be evolved in the form of heat if you want to get rid of five pounds of this fat by combustion? (c) How many nutritional calories is this? (1 nutritional calories =1103 calories)