CHEM 120 FINAL EXAM QUESTIONS AND CORRECT ANSWERS LATEST UPDATE 2024 (GRADED A+)

CHEM 120 FINAL EXAM QUESTIONS AND CORRECT ANSWERS LATEST UPDATE 2024 (GRADED A+) what is compressability - Answers gases have larger spaces between them which makes them very compressible what are the 4 parameters for describing gas - Answers pressure, temperature, moles, volume what is pressure - Answers force exerted per unit area on walls of container What is atmospheric pressure? - Answers force exerted by the atmosphere= 101.3 kPa What is a barometer? - Answers An instrument that measures atmospheric pressure What is a manometer? - Answers instrument used to measure gas pressure compared to atmospheric pressure What is STP? - Answers Standard temperature and pressure T= 0 celsius/ 273 K P= 1 bar what is boyles law - Answers at constant P, as volume goes up, pressure goes down what can you say about stoichiometry of gases - Answers under constant T&P volumes are proportional to stoichiometric coefficients nA+nB = nTotal What is Dalton's Law? - Answers "Partial Pressures" The total pressure of a gas mixture is equal to the sum of the pressure that each gas would exert independently what kind of collisions do gas particles undergo - Answers completely elastic Explain Maxwell-Boltzmann distribution. - Answers um = most probable speed @ highest # of particles (vertex) uav = average speed urms= root mean square velocity *um uav urms* compare molar mass and urms - Answers as molar mass increases, urms decreases compare temperature and urms - Answers as temperature increases, urms increases Define effusion - Answers A process by which gas particles escape through a tiny opening into a vacuum Define diffusion - Answers random movement of molecules in space due to concentration difference (high conc to low) what is excluded volume in non-ideal gases - Answers the volume occupied by the gas molecules (b) what is interaction potential in non-idea gases - Answers real gas molecules attract each other at short distances (a) what happens when the excluded volume is high? - Answers higher pressure what happens when intermolecular attraction is high? - Answers lower pressure when will a gas behave ideally? non-ideally? - Answers ideally: high temp, low pressure. non-ideally: low temp, high pressure. what is the compressibility factor and what does its value mean - Answers z=1 the gas behaves ideally z1 excluded volume dominates (P(nRT/v)) z1 attractive forces dominate (P(nRT/v)) What is the rate law equation? - Answers rate = k[A]^m[B]^n what is the overall reaction order - Answers sum of the exponents m+n what graph is linear for a zero order reaction - Answers [A] vs time what graph is linear for a first order reaction - Answers ln[A] vs time what graph is linear for a second order reaction - Answers 1/(ln[A]) vs time what increases with temperature in chemical reactions - Answers kinetic energy; # of collisions, frequency of collisions what increases with concentration in chemical reactions - Answers # of collisions, frequency of collisions what is activation energy (Ea) ? - Answers the minimum kinetic energy needed to initiate a reaction What does the rate of reaction depend on? - Answers 1) collision frequency 2) orientation of molecules 3) fraction of molecules that have KE Ea formula for enthalpy of reaction - Answers ΔHr = ΔHprod - ΔHreact what does the reaction profile of an endothermic reaction look like? - Answers x- reaction progress y- potential energy starts at reactants (lowest PE), increases to its transition state (peak), decreases to products (middle PE) how do you read EaFWD from an endothermic reaction profile - Answers the distance from reactant PE to the transition state how do you read EaREV from an endothermic reaction profile - Answers the distance from product PE to the transition state what is ΔH in an endothermic reaction profile - Answers EAfwd - EArev what does the reaction profile of an exothermic reaction look like? - Answers x- reaction progress y- potential energy starts at reactants (middle PE), increases to its transition state (peak), decreases to products (lowest PE) how do you read EaFWD from an exothermic reaction profile - Answers the distance from reactant PE to the transition state how do you read EaREV from an exothermic reaction profile - Answers the distance from product PE to the transition state what is ΔH in an exothermic reaction profile - Answers ΔH = EArev - EAfwd what gets cancelled out in reaction mechanisms - Answers intermediates, they get produced and then consumed in the next step what is the rate determining step in a reaction mechanism - Answers the slowest one, lowest k what is the rate law when the first step is rate determining - Answers rate = k1 [reactant][reactant] what is the rate law when the initial step is fast - Answers the rate law will be rate = kn[reactant][reactant] of the slowest step but there will be an intermediate in the rate law! therefore you must use eqn 1: equate the fwd and rev rxn and isolate for the intermediate to find an expression of it in terms of non-intermediates. sub this in for the intermediate in the rate law and simplify! when do you use steady state approximation - Answers when you don't know which step is the slow one. explain the steps of steady state approximation - Answers 1) assume the first rxn is reversible 2) identify the intermediate and break down the rates of formation and consumption for the INTERMEDIATE 3) set the two equal to eachother and solve for the intermediate 4) sub the intermediate expression into the presumed rate law of step 2 what does catalysis do - Answers adding catalysts- lowers the activation energy what is homogeneous catalysis - Answers catalysts are in the same state as reactants what is heterogenous catalysis - Answers catalysts in a different state than reactants, usually solid, providing an "active site" what is an enzyme substrate treated like in rate laws - Answers treated as an intermediate, therefore use steady state approximation on it to find the rate law what is an open system - Answers a system that exchanges matter and energy with its surroundings what is a closed system - Answers a system that only exchanges energy with its surroundings what is an isolated system - Answers a system where no matter or energy is exchanged with surroundings what is energy - Answers the capacity to do work what is kinetic energy - Answers energy of motion what is potential energy - Answers energy of position what is work - Answers force acting over a distance what is heat - Answers the quantity of energy transferred between a system and its surroundings because of temperature difference what is thermal equillibrium - Answers when heat stops flowing- ΔT=0 what is internal energy of a system (u)? - Answers u = KE + PE and it is always conserved what direction does heat flow - Answers warm to cold When is work negative and positive? - Answers w = (-) when system is DOING work. w = (+) when system is RECEIVING work. when is heat negative and positive? - Answers q = (-) when system is losing heat q = (+) when system is gaining heat explain pressure-volume work - Answers work is done BY an expanding gas. work is done ON a compressing gas. What is a state function? - Answers a function that only depends on the initial and final states of the system, not how it got there. Almost everything in thermodynamics is a state function EXCEPT work (w) and heat(q) what is heat capacity (C) - Answers amount of heat req to change temp of a system by 1K What is specific heat capacity? (c) - Answers amount of heat req to change the temp of 1g of a substance by 1K. what is molar heat capacity (Cm) - Answers amount of heat req to change the temp of 1mol of a substance by 1K. What is a calorie? - Answers the amount of heat needed to raise the temperature of 1 gram of water 1 degree Celsius what is an calorimeter - Answers device used to measure the amount of heat released or