Chem 1V CH.6
If the chemical formula for coal is C135H96O9NS, what is the mass % of N? Multiple choice question.
0.73 Reason: (14 g/mol / 1906 g/mol) x 100% = 0.73%
A slice of pizza supplies 217 kcal (217 Cal). If a person weighing 140 lb expends 80 kcal per mile when walking at 2.0 miles per hour, approximately how long will it take to use up the calories from the pizza? Multiple choice question
1 hour 20 minutes 217 kcal x 1mile80kcal1mile 80kcal x 1hr2miles 1hr2miles = 1.36 hr or 1 hour 20 minutes
A 1 oz piece of dark chocolate supplies 720. kJ of energy. Convert this to kcal (nutritional calories or Cal) given that 1 kJ = 0.239 kcal.
172cal
If the chemical formula for coal is C135H96O9NS, what is the %O? Multiple choice question.
7.6% Reason: To calculate the %O, you would consider the atomic mass of O (16 g/mol) and the overall molar mass of the compound (1906 g/mol): ((9 x 16)/1906) x 100% = 7.6%
Endothermic
A reaction that absorbs heat
Exothermic
A reaction that releases heat
Which of the following statements correctly describes bond energy? Select all that apply. Multiple select question
Bond energy values are always positive. The total energy required to break apart a molecule depends on the number and type of bonds.
Which of the following are common products of combustion? Select all that apply.
CO2, H2O
The complete combustion of hydrocarbons in oxygen produces _____ and water, whereas incomplete combustion when the supply of oxygen is limited is more likely to produce ______.
CO2: CO
True or false: Energy is required to form bonds.
False
Which of the following are considered exothermic processes? (Select all that apply.)
Freezing water Burning a fuel
Which of the following options correctly describe temperature and heat?
Heat always flows from the hotter object to colder ones Temperature is a measure of the kinetic energy of molecules
Which of the following options correctly describes an exothermic reaction? Multiple choice question
It releases more energy by forming product bonds than is needed to break reactant bonds.
What is the modern metric unit of energy?
Joules (J)
Which of the following options correctly describes activation energy? Select all that apply.
Lower activation energy generally results in faster reactions. Increasing temperature allows more particles to have sufficient energy to overcome the activation energy barrier.
Which of the following are common sources of energy in the United States? Select all that apply.
Natural gas Petroleum Coal
Which of the following are common oxidizing agents in combustion reactions? Select all that apply.
O2 (g) H2O2 (l) O3 (g)
Which of the following options correctly describes exothermic and endothermic reactions? Select all that apply.
The energy change for an endothermic reaction has a positive sign. Exothermic reactions produce heat when they occur.
How is a calorie defined?
The energy needed to increase the temperature of 1 g of water by 1 oC
Which of the following are forms of potential energy? Select all that apply. Multiple select question
The energy stored in the chemical bonds of a compound The energy of an object suspended above the ground
What is the most common effect of increasing temperature on a chemical reaction?
The reaction rate will increase.
Which of the following can be used to determine the heat released by a combustion reaction performed in a calorimeter?
The temperature increase of the calorimeter system
True or false: Energy is required to break bonds.
True
London dispersion forces _______. (Select all that apply.) Multiple select question
are intermolecular attractions are stronger for larger molecules than smaller ones are much weaker than the covalent bonds within the hydrocarbon molecule
Energy is required to (break/form) bonds, whereas energy is released when bonds are (broken/formed) .
break; formed
Combustion is best described as ________.
chemical reaction with oxygen to release energy. Combustion is rapid combination with oxygen to release energy in the form of heat and light.
When a molecular substance evaporates (passes from the liquid to the gas phase), the _____ within each molecule remains intact, but the _____ are broken.
covalent; intermolecular attractions
The ability to do work or produce change is called ______.
energy
Kinetic energy
energy of motion
Converting a substance from liquid to solid states is considered an (exothermic/endothermic) process. The conversion from liquid to gaseous states is considered an (exothermic/endothermic) process.
exothermic; endothermic
A controversial method known as_______ is used to extract natural gas and oil from rocks far below the surface of the Earth using the injection of a high-pressure liquid.
fracking
A calorimeter is used to measure the_______ released or absorbed by a reaction.
heat
Compounds containing only carbon and hydrogen are called .
hydrocarbons
Attractions between individual molecules are called _______attractions.
intermolecular
The ease with which a liquid evaporates depends on the strength of its intermolecular forces. A liquid with stronger intermolecular forces will have a ______ vapor pressure at a given temperature and thus a ______ boiling point.
lower; higher
An_______ agent is needed for combustion, alongside a fuel and ignition source.
oxidizing
Hydrocarbons with only _______bonds between carbon atoms are called alkanes.
single; sigma
Potential energy
stored energy or energy of position
A liquid will have a higher boiling point if its intermolecular attractions are ______.
stronger
The bond energy of a C-H bond is _____.
the amount of energy consumed to break a C-H bond
Activation energy is best described as _____.
the energy required to initiate a chemical reaction
Heat
the flow of energy between objects with different molecular kinetic energies
Temperature
the measure of the average kinetic energy of the atoms/molecules in a substance
The boiling point of a liquid is the temperature at which _______.
the vapor pressure of the liquid equals the external pressure
A liquid can evaporate at any temperature, producing vapor above the surface of the liquid. This vapor exerts pressure, which is called the______pressure. This pressure________as the temperature of the liquid increases. When this pressure equals the external pressure, the liquid has reached its boiling point.
vapor; increases or rises
Energy is the ability to do ________ or to produce________.
work; change
