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# Chemistry formulas

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### Chemistry formulas

1. 1. Chemistry formulae Ideal Gas law PV = nRT n = number of moles P1V1 = P2V2 R = universal gas constant = 8.3145 T1 T2 J/mol K Combined Gas law Boyles law P1V1 = P2V2 V1 = V2 T1 T2 Charles law Diffusion: Rate at which two gases mix P1 = P2 Grahams law of diffusion T1 T2 The rate of diffusion of a gas is inversely Gay-Lussac law proportional to the square root of their density or the molar mass of the gas. Effusion: Rate at which a gas Solution: Solution is a homogeneous escapes thru pin hole mixture of two or more substances. Grahams law of effusion Solute is a substance that is dissolved in The rate of effusion of a gas is the solution. inversely proportional to the square Solvent is the substance that dissolves the root of either the density or the molar solute. Solvent is present in greater mass of the gas. amount.
2. 2. Concentration is the ratio of solute Unit of Morality (M) : mol/L : moles per literand solvent. Unit of Morality (M) : mol/kg : moles perConcentration can be measured using kgmorality, morality and mole fraction.Morality (M) = moles of solute liters of solutionMorality (m) = moles of solute kg of solutionMole fraction: Mole fraction of a Dilution: Diluting a solution means addingcomponent in solution is the number of more solvent in solution without the additionmoles of that component divided by of more solute.the total number of moles of allcomponents in the solution. MiVi = MfVf Mi: Morality of solution before diluting. Vi: Volume of solution before diluting. Mf: Morality of solution after diluting.
3. 3. molesa Vf: Volume of solution after diluting.Mole-fraction (Xa)= molesa + molesb ....Mole: Mole is the amount of One mole of gas has volume of 22.4 litersubstance that contains same number at STP.of particles as there are atoms inCarbon-12. One mole of substance isAvogadros number (i.e. 6.023 x 1023).Relation between moles and grams Ionization Enthalpy: It is the energy1 mole = molecular weight of needed to remove an electron from an atomsubstance in grams. or molecule (i.e from low state to n=∞). It is always endothermic (i.e. positive).OR Ionization energy: energy needed to remove an electron from an atom [A-]pH = pKa + log10 [HA]Henderson-Hasselbalch equation:where[A-]: Concentration of conjugate base[HA]: concentration of the acidOR [Conjugate Base]pH = pKa + log10 [Acid]
4. 4. Ideal Gas LawThe ideal gas law is given by: PV = nRTWhere:P: the absolute pressure of the gasV: volume of the gasn: number of moles, which is the ratio of mass and molar massR: universal gas constant, which is R = 8.3145 J · mol-1 · K-1T: the absolute temperatureHenrys LawHenrys law is given by: p = K · xWhere:p-partial pressure of the solute , H – Henry’s ConstantHess LawHess Law can be expressed in 3 ways and they are:For enthalpy we have:For entropy we have:For Gibbs free energy we have:Raoults Law
5. 5. Raoults law is given by: Pi = xi - Pi *Where: Pi pressure of component , xi – mole fraction in the solution , Pi * - vapourpressure of the pure substance. i.In a solution with two liquids A and B, if no gas are present, the total vapor pressure isgiven by:Ptot = PA + PBWhere: PA – vapor pressure of liquid A , PB – vapor pressure of liquid BFor an ideal solution of liquids A and B, which obeys Raoults law over the full range ofcomposition. The total pressure is given by:ptot = xA pA* + xB pB* , where xA + xB = 1Molar EnthalpyHm = H / nWhere: H: enthalpy; n: number of molesMolar MassThe molar mass equation is given by; M=Mr.g. mol-1Where:M: molar mass, which is the mass of one mole of a substanceMr. Relative molar mass, also called molecular weight This equation is obtained from the following equation:Where:
6. 6. NA: Avogadro Constant which is NA = 6.0221·1023mol-1mu: molar mass constant, which is mu = 1 g · mol-1DilutionTo calculate dilution, we can use the following formula: M1 * V1 = M2 * V2Where: M: Morality which is given by: M = n/NA which is given by: M = n/NA V: VolumeMorality (M): Moles of Solute/Liters of solutionUnit of Morality (M): mol/L ; moles per litersMoles of Solute/Liters of solutionEnthalpy The enthalpy is given by the formula: H = U + pVWhere: H: Enthalpy U: Internal energy p: pressure V: volume Gibbs ‘Free Energy Gibbs’ free energy is given by: ΔG = ΔH- TΔSWhere:
7. 7. H: Enthalpy T: Temperature S: entropyTemperature ConversionTo convert between Kelvin and Celsius you can use the following formulas: • From Kelvin to Celsius : °C= K - 273 • From Celsius to Kelvin: K = °C + 273