EduCalc Classic Pro vs Thermochemistry Usage & Stats

** I recommend buying EduCalc Pro instead of this app. That said, I will be maintaining this app. ** Features: 1) Scientific Calculator. A lot of thought has gone into the design of the keyboard, which gives you everything you need while keeping the keys as large as possible. Available functions include the following: • the usual arithmetic functions and exponentiation. • square root, cube root, nth root, natural log, log base 10, log of arbitrary base, absolute value, factorial, permutations (nPr), combinations (nCr), modulus, random integer, bell curve, cumulative normal distribution. • Define and name your own constants • Summations • Complex numbers! • Sig figs (requires iOS 6; enable under settings) • Programmable keys (enable under settings) 2) Graphing. Capabilities: • Graph up to nine equations at once. • Graphs are labeled. • You can drag the graph or pinch to zoom in or out. • Calculator can find roots and intersections. • Can graph in polar coordinates. • Can graph parametric equations. • Can graph parametric equations. • Can graph implicit functions, such as x^2+y^2-4=0. Most calculator apps can't do this! 3) Vector and Matrix calculator. Vector dot and cross products. Multiply and add matrices. Determinant, transpose, Eigenvalues and Eigenvectors. 4) It can make a table of the values of any function you care to enter. You can choose the starting x value of the table, as well as how much x increases for each successive row. 5) Triangle solver. Enter three sides, two sides and an angle, or two angles and a side, and the solver calculates the rest. 6) Polynomial solvers. Find roots of linear, quadratic, or cubic polynomials. 7) The reference hits the high points of the following subjects: algebra, calculus, geometry, trigonometry, vectors, vector calculus, and classical mechanics. So if you need a reminder of a trig identity . . . or the quadratic formula . . . or the chain rule from calculus . . . and so on, it's right there for you. 8) A unit converter. Your data are in meters, and you need an answer in feet? No problem! With a tap, you can enter the result of your conversion into the calculator. Currently converts different units of the following: acceleration, angle, area, density, distance, energy, force, mass, power, pressure, speed, temperature, time, and volume. Great for physics problem sets! You can also define your own units. 9) Constants for scientific calculations -- speed of light, strength of gravity at Earth's surface, etc. etc. etc. Tapping on a constant will insert it into your calculation -- i.e, you don't have to key in the value. Again, great for physics problem sets! 10) Statistics mode, including options for scatter plots and for regression lines. 11) Works on both iPhone and iPad. *** Note about the screenshots -- if you are viewing this in iTunes, you can see 10 different shots across the 2 different devices. They are all different shots. We need that many to show the range of capabilities of the calculator; even still we are leaving some things out. *** I'd love to learn about your comments or suggestions. You can write me at jockuxyzsch@gmail.com -- but without the xyz. Thanks!

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Thermochemistry

Thermochemistry helps in evaluation of enthalpy or heat release/absorption of a system undergoing numerous temperature changes and phase transitions. The calculations take advantage of known values of heat capacity at constant pressure (Cp) and molar or per gram enthalpy of phase transition. Amount of compound can be defined in grams or moles, in a way that Cp and enthalpy units would match. App provides enthalpy values for each step. Negative enthalpy points to exothermic process – heat release, while positive one to endothermic - heat absorption. °C and K are interchangeable. Calorimetry section provides means for evaluation of the heat capacity of calorimeter and for finding equilibrium temperature of mixed system. Forward arrow button sets the final temperature of the mixture. Backward arrow button sets missing temperature or heat capacity of one of the components. Enthalpy values show heat flow for each component. Example of problems solved by application (screenshots): Problem 1: Calculate the amount of energy required to change 100.0 g of ice at -15.0 °C to steam at 125.0 °C. Known values: Heat of melting = 334.16 J g¯1 Heat of vaporization = 2259 J g¯1 specific heat capacity for solid water (ice) = 2.06 J g¯1 K¯1 specific heat capacity for liquid water = 4.184 J g¯1 K¯1 specific heat capacity for gaseous water (steam) = 2.02 J g¯1K¯1 Solution: 1) Heating of 100.0 g of ice from -15.0°C to 0.0°C: (100.0 g) (15.0 K) (2.06 J g¯1 K¯1) = 3090 J 2) Melting of 100.0 g of ice: (100.0 g) (334.16 J g¯1) = 33416 J 3) Heating of 100.0 g of liquid water from zero to 100.0 Celsius: (100.0 g) (100.0 K) (4.184 J g¯1 K¯1) = 41840 J 4) Evaporations of 100.0 g of liquid: (100.0 g) (2259 J g¯1) = 225900 J 5) Heating of 100.0 g of steam from 100.0 to 125.0 Celsius: (100.0 g) (25.0 K) (2.02 J g¯1 K¯1) = 5050 J 6) Summation of the results: 3090 + 33416 + 41840 + 225900 + 5050 = 309.3 kJ Problem 2: Determine the heat capacity of a coffee-cup calorimeter. During calibration 100.0 g of water at 58.5 °C has been added to 100.0 g of water, already in the calorimeter, at 22.8 °C. Calculate the heat capacity of the calorimeter in J/°C, if final temperature of the water is 39.7 °C. (Specific heat of water is 4.184 J/g °C.) Solution: 1) Heat given up by warm water: q = (100.0 g) (18.8 °C) (4.184 J/g °C) = 7865.92 J 2) Heat absorbed by water in the calorimeter: q = (100.0 g) (16.9 °C) (4.184 J/g °C) = 7070.96 J 3) The difference was absorbed by the calorimeter: 7865.92 - 7070.96 = 794.96 J 4) Calorimeter constant: 794.96 J / 16.9 °C = 47.0 J/°C Problem 3: Determine the final temperature when 10.0 g of aluminum at 130.0 °C mixes with 200.0 grams of water at 25.0 °C. Please note the starting temperature of the metal is above the boiling point of water. In reality, the sample may vaporize a tiny amount of water, but we will assume it does not for the purposes of the calculation. Solution: 1) The colder water will warm up and the warmer metal will cool down. The whole mixture will equilibrate up at the same temperature. The energy which "flowed" out of the warmer metal equals the energy which "flowed" into the colder water: Qaluminum = Qwater (10) (130 - x) (0.901) = (200.0 )(x - 25) (4.18) 117.13 - 0.901x = 83.6x - 2090 x = 26.12 °C. Important! Water didn’t cross temperature of phase transition – vaporization; otherwise calculation would be more complex. Calculation of reaction standard Gibbs free energy: For the general reaction aA + bB -> cC + dD ΔG°rxn = cΔGf°(C) + dΔGf°(D) - aΔGf°(A) - bΔGf°(B) Example: Calculate the Gibbs free energy for the following reaction at 25 °C. Cu (s) + H2O (g) -> CuO (s) + H2 (g) ΔG°rxn = ΔGf°(CuO (s)) – ΔGf°(H2O (g)) = (–129.7 kJ/mol) – (–228.6 kJ/mol) = 98.9 kJ/mol ΔGf° = 0; for elements in their standard state by definition. At equilibrium, ΔG = 0! Important points Application uses dot as a decimal separator. Special attention should be paid for units’ consistency.