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Chem Exam 3
| Question | Answer |
|---|---|
| Equation for pressure | F/A; force/area; Newton (N)/m^2 |
| Force equation | F=m*a (Force is weight times the speed/gravitational pull) |
| SI unit of force | Newton (N) |
| SI unit of Pressure | Pascal (Pa) |
| 1 atm to Pascal | 1.01325x10^5 Pa (101,325 Pascal) (will be given) |
| 1 atm to mmHg (mm of Mercury) | 760 mmHg (will be given) |
| 1 torr to 1 mmHg | 760 mmHg (will be given) |
| Pressure related to column heights | (first)h*d=(Second)h*d |
| 1 torr to atm | 1/760 atm (will be given) |
| Water can only be pumped up to | 33.91 ft |
| Gas pressure measuring device | Manometer |
| Atmosphere pressure measuring deviced | Barometer |
| Robert Boyle | Relationship of gas: V=(R)1/P (Volume increases, Pressure decreases) -- VP=k "Boyles Beer Can - As it empties, pressure outside crushes it" |
| Boyle's constant equation (Boyle's Beer Can) | P1V1=P2V2; the constance of both states are equal. (Use if the n & T are constant) |
| Charles' Law (Charles in Charge) | For VARIOUS pressure, volume increases with temperature. V=(R)T (Because the n & P are constant) "Charles in Charge on TV" |
| If you change pressure you only see a slope of the line in | Temperature |
| Extrapolation (imaginary line) for any gas pressure to temperature is alway 0 at what temp? | -273.15 C |
| Lord Kelvin (William Thomson) | 0 Kelvin = -273.15 C (will be given); coldest possible temperature, because negative gas volume is not possible. |
| Gay-Lussac Law (Toilet paper) | As temp increases, so does pressure. Pressure = (R)Temperature. (Use if the Volume and n are constant) "T P" |
| Avogadro's Law (dreamy bod) | Volume = n (number of moles) (Use if the P & T are constant) "His volume is always constant" |
| Ideal gas Equation (All four laws together): | PV=nRT - If we know P, V, & T, we can determine n, because R is constant |
| R (constant in L*atm) | .08206 L*atm/mol *Kelvin (will be given) |
| R (constant in Joules) | 8.314 J/mol *Kelvin (will be given) |
| Overall mass of the gas - weigh the gass | Mass (m)/'n' Moles of gas = molar mass (M). Use Ideal Gas Equation to find 'n' moles. (m/M=n) |
| Density of a gas | D=m/volume=(m/M)/V); Use Ideal Gas Equation: PV=nRT > n/V=(P/RT)> *(m/M)/V=(P/RT)* (OR D is (m/V)=MP/RT |
| Partial Pressure (Dalton's Law) | "Divvying a Ton"; Ideal Gas Equation: P=(nRT/V) > can use for n moles of each to find partial pressure of each, then add to find total P |
| Mole Fractions and Partial Pressure | The moles of one divided by the total moles. Use this % to find same partial pressure % of total pressure. (% of total pressure = Partial Pressure) |
| Kinetic Molecular Theory of Gas provides | An Explanation of the gas laws |
| Kinetic Molecular Theory of Gas: Basics Postulates by: | Rudolf Clausius > Basic posers: Rudolf and Santa Claus |
| 4 Basic Postulates: | 1.Gas molecules (GM) are far apart (mostly empty space); 2.GM have large # of molecules in constant random motion (Collisions pass NRG, but never increase or decrease); 3.GM move in straight trajectories, do not attract or repel; 4. Avrg. KE(nrg)=K(temp) |
| SI Units of Energy: | Joule (J)=(kg*m^2)/s^2; NOT a base unit. Derived from kg. (will be given) |
| Kinetic Energy | KE: 1/2(m*v); m=mass(grams) v=velocity(meter/second) OR V=Average speed (u^2) <--- KNOW THIS; u^2 conversions will not be provided for exam |
| Average Speed | U^2: Sum of the speed of molecules/number of molecules; <--- KNOW THIS; u^2 conversions will not be provided for exam |
| Total Kinectic NRG of one mole of gas: | KE=(3/2)RT; R=8.314 J/mol*K (will be given) |
| Molecular speed of gas is... | Random: broad distribution of KE, different molecular speeds. Maxwell-Boltmann (He knows how gases 'bolt' around) |
| Lower the T (temp), the ____ gas particles are moving on average (KE) | Slower |
| U(rms) is... | Average root-mean-square; sqrt(3RT/M) (equation will be given); R=(8.314Kg*m^2)/(s^2*K*mol) (given, but need to know the constant to use is moles, since you're measuring the speed of moles, not NRG - or joules) |
| What are the U(rms) molecular speeds for Nitrogen (N2) gas at 25 °C and 625 °C ? Use the average root-mean-squared. | urms(298 K) = 515 m/s; urms(898 K) = 894 m/s; Remember to convert to Kelvin. M=molecular mass of 2 Nitrogen atoms IN KILOGRAMS. m^2/s^2 is m/s after sqr root. |
| Smaller the molecules, the _____ their molecular speed. | Faster |
| Pressure of a gas is due to the ... | Collisions of the gas molecules on the container walls. |
| Increase the ________, both the NRG(force) of collisions and the frequency of collisions increase, resulting in higher pressure. | Temperature |
| Reduce _____, increases gas concentration, increasing the collision frequency and increases pressure. | Volume |
| Mixing of Gases | Diffusion: Constant random motion of gas molecules diffuse from high partial pressure to low partial pressure. (gas is anti-social. And they stink. Moves to lower concentrated area) |
| Gas diffusion is like state functions (football) because | Molecules bump around for thousands of miles, just to get from one side of the room to the other. |
| Graham's Law of Diffusion | Rate of diffusion is inversely proportional to the sqrt of their molar mass. r1(gas 1)/r2(gas 2)=sqrt (molar mass 1/molar mass 2); Equation will be given, but need to know molar mass is periodic weight in KILOgrams/mol. |
| Lighter isotopes diffuse/effuse _______ than heavier isotopes. | Faster |
| Effusion | The escape of gas molecules through a tiny hole into an evacuated space. (memory tool: Takes more "effort" - doesn't actually, follows the same rule of diffusion, but there you go.) Also, R=Joules in U(rms) equ. More effort to remember. |
| Ideal vs Real Gases (2:1) | Ideal (PV=nRT): 1. Molecules have no molecular volume, 2. Molecules have no attractive or repulsive forces (ions); Real gases: 1. Have a molecular volume and finite attractive forces between molecules. |
| Real Gas Equation (Van der Waals) | Do not need to know equation, but know that increased attraction decreases pressure and molecular volume reduces "free" volume. |
| Chemical _________ involve changes in energy. | Reactions |
| Energy: Not a _______ thing that can be weighed and bottled. | Physical |
| Energy is an ________ possessed by things, the _________ to do work. | Ability |
| Potential Energy | Energy in position (not in motion). |
| Kinetic Energy | Energy in motion |
| Chemical Energy | Stored energy due to natural attractions or repulsions of atoms. |
| 1 Kilojoule = _____ Joules | 1000 |
| 1 calorie (cal) = _____ Joules | 4.184 |
| 1 Kilojoule - _____ cal | 1000 |
| 1 Kilocalerie = _____ food cal | 1 |
| 1st Law of Thermodynamics | Energy cannot be created nor destroyed, but stays constant within the universe. (conservation) |
| Thermodynamics Terms: System | The particular component under study (chemical reaction) |
| Thermodynamics Terms: Surroundings | Everything else but the system |
| Thermodynamics Terms: Universe | Everything (system + surroundings) |
| Thermodynamics Terms: Open System | Allows for the exchange of mass (gas/vapor) and energy (heat) with the surroundings. (open bottle) |
| Thermodynamics Terms: Closed System | Allows for the transfer of energy (heat), but not mass (gas/vapor) with the surroundings (closed bottle) |
| Thermodynamics Terms: Isolated system | Does NOT permit the transfer of mass (gas/vapor) or energy (heat) with the surroundings. (Insulated) |
| Internal Energy | The total Kinetic and potential energy of a system. NOT ABSOLUTE. Measured change from initial state to final state. |
| For a chemical reaction, initial state is | Reactants |
| For a chemical reaction, final state is | Products |
| For a chemical system, the change in internal energy is related to the ____ added or removed from the system, plus the work done on or by the system. | Heat |
| First Law of Thermodynamics: Changes in internal NRG of a system to transfer of heat and work is what equation? | ΔEnergy = heat (q) + work (w) (will be given) |
| If heat (q) is added to the system (in the reactants), q is (+ or -?) | q+ |
| If heat (q) is removed from the system (in the products), q is (+ or -?) | q- |
| If work (w) is done on the system (ie. System is compressed - larger molecules in the products), w is (+ or -?) | w+ |
| If work (w) is done by the system (ie. System expands - smaller molecules in the products), w is (+ or -?) | w- |
| Mechanical Work of a chemical system involves the _________ of a gas against a constant pressure. | Expansion; |
| Work = | (-)Pressure*ΔVolume; If asked in Joules, use conversion given of 1atm*L=101.325 Joules |
| Exothermic Reaction | When a reaction gives off heat into its surroundings (work is -, molecules in the product are smaller, heat/energy is given off). "Exo-Exit" |
| Endothermic Reaction | When a reaction has gained heat from it's surroundings (work is +, molecules in the product are bigger, heat/energy was added) "Endo-delivered" |
| Two Sets of reaction conditions: | 1. Open container - under constant pressure (atm pressure); 2. In a closed rigid container - constant volume, variable pressure. |
| Heat Energy is called | Enthalpy, when the system is at constant pressure. "Because without heat energy, everything goes into Entropy (chaos)" |
| Temperature and Pressure conditions of STP are.... | 0 degrees Celsius and 1atm |
| At a constant volume (sealed, rigid container), there is ______ work done. | No; W=-P*ΔV ; If volume is 0, work is 0. In a vacuum, no work is done. |
| Extensive property means | Property that depends on quantity of matter. (Heat is an extensive property) |
| A gas expands and does PV work on its surroundings equal to 332 J. At the same time, it absorbs 138 J of heat from the surroundings. Calculate the change in energy of the gas. Note: PV work means work done by a changing volume against constant pressure. | ΔU = −1.94 × 102 J; ΔU=q+w; heat is absorbed, so it's +, but work is done on surroundings, so it's - |
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