1.
The SI unit of heat and energy is the __________.
Correct Answer
D. Joule
Explanation
The SI unit of heat and energy is the joule. The joule is a derived unit of energy in the International System of Units (SI). It is defined as the amount of energy transferred when a force of one newton is applied over a distance of one meter. Heat is a form of energy, and the joule is commonly used to measure both heat and other forms of energy. The calorie is a non-SI unit commonly used to measure heat, but the joule is the preferred unit in scientific and engineering contexts. The watt is a unit of power, which is the rate at which energy is transferred or converted.
2.
Temperature is a measure of the average ______ energy of individual atoms.
Correct Answer
B. Kinetic
Explanation
Temperature is a measure of the average kinetic energy of individual atoms. Kinetic energy refers to the energy an object possesses due to its motion. In the context of temperature, it is the random motion of atoms or molecules that determines the temperature of a substance. As temperature increases, the average kinetic energy of the atoms also increases, leading to greater molecular motion and higher temperatures. Therefore, the correct answer is kinetic.
3.
A catalyst works by
Correct Answer
B. Lowering the activation energy
Explanation
A catalyst works by lowering the activation energy required for a chemical reaction to occur. Activation energy is the minimum amount of energy needed for reactant molecules to collide with enough force to undergo a chemical transformation. By lowering this energy barrier, a catalyst enables the reaction to proceed more easily and at a faster rate. It does not increase the temperature or change the order of the reaction, but rather provides an alternative pathway for the reaction to take place, making the formation of the activated complex more favorable.
4.
N_{2} + 3H_{2} --> 2NH_{3}
How many moles of ammonium is produced when 3 moles of nitrogen react with hydrogen?
Correct Answer
B. 6 moles Ammonium
Explanation
When 3 moles of nitrogen react with hydrogen according to the balanced equation N2 + 3H2 -> 2NH3, it can be observed that for every 3 moles of nitrogen, 2 moles of ammonia are produced. Therefore, if 3 moles of nitrogen react, the corresponding amount of ammonia produced would be (3 moles nitrogen / 3 moles nitrogen) * 2 moles ammonia = 2 moles ammonia. Thus, the correct answer is 2 moles Ammonium.
5.
______ is the amount of energy required to raise the temperature of 1 gram of any substance 1^{o}C.
Correct Answer
D. Specific heat
Explanation
Specific heat is the amount of energy required to raise the temperature of 1 gram of any substance by 1oC. It is a property that is unique to each substance and is often used to characterize and compare the heat-absorbing or heat-releasing abilities of different materials. The specific heat of a substance determines how much heat energy is needed to cause a temperature change in that substance.
6.
A 200ml of water is heated by the burning of a biscuit. If the ΔT=45.6^{0}C and the change in mass of the biscuit, Δm =5.35g.Find the enthalpy of the biscuit in kJ/g. (Q=mcΔT)
Correct Answer
A. 7.13
Explanation
The enthalpy of the biscuit can be calculated using the formula Q=mcΔT, where Q is the heat transferred, m is the mass of the biscuit, c is the specific heat capacity of water, and ΔT is the change in temperature. In this case, the change in temperature is given as 45.6°C and the change in mass is given as 5.35g. The specific heat capacity of water is approximately 4.18 J/g°C. By substituting these values into the formula, we can calculate the enthalpy of the biscuit, which is approximately 7.13 kJ/g.
7.
H_{2} + ½ O_{2} --> H_{2}O + 285kJ is an example of a(n)
Correct Answer
B. Thermochemical equation
Explanation
The given equation represents a chemical reaction in which hydrogen gas (H2) and oxygen gas (O2) combine to form water (H2O) with the release of 285 kJ of energy. This type of equation is known as a thermochemical equation because it involves the measurement and calculation of heat energy changes during a chemical reaction. Thermochemical equations are used to represent the energy flow in chemical reactions and provide information about the enthalpy change (heat released or absorbed) associated with the reaction.
8.
How much heat does an aluminum block absorb if 10.00 grams are heated from 25.0^{o}C to 50.0^{o}C? The specific heat of aluminum is 0.900J/g^{o}C.
Correct Answer
A. 225
Explanation
When an object absorbs heat, the amount of heat absorbed can be calculated using the equation Q = mcΔT, where Q is the heat absorbed, m is the mass of the object, c is the specific heat capacity, and ΔT is the change in temperature. In this case, the mass of the aluminum block is given as 10.00 grams, the specific heat of aluminum is given as 0.900 J/goC, and the change in temperature is 50.0oC - 25.0oC = 25.0oC. Plugging these values into the equation, we get Q = (10.00 g)(0.900 J/goC)(25.0oC) = 225 J. Therefore, the correct answer is 225.
9.
C+ O_{2} --> CO_{2} + 60kJ, what is the value for ΔH for the reaction?
Correct Answer
C. -60
Explanation
The value for ΔH for the reaction is -60. This is because the reaction is exothermic, as indicated by the positive value for the release of energy (60 kJ). In an exothermic reaction, the products have a lower energy level than the reactants, resulting in a negative ΔH value. Therefore, the correct answer is -60.
10.
How much heat is needed to form 40.0 L of NO_{2} from its elements at STP?
V_{m}=22.4L
N_{2}+ 2O_{2} -> 2NO_{2}
ΔH = +67kJ
Correct Answer
A. 59.8
Explanation
The correct answer is 59.8. The equation given is N2 + 2O2 -> 2NO2. This means that for every 1 mole of N2, 2 moles of O2 are needed to form 2 moles of NO2. Since the volume of NO2 is given as 40.0 L, which is equal to 2 moles of NO2 (since 1 mole of gas occupies 22.4 L at STP), we can conclude that 1 mole of N2 and 2 moles of O2 are needed to form 40.0 L of NO2. The enthalpy change for the reaction is given as +67 kJ. Therefore, to find the heat needed to form 40.0 L of NO2, we can use the equation: (67 kJ / 2 moles) x 1 mole = 33.5 kJ. Converting kJ to J, we get 33,500 J, which is equal to 59.8 kJ.