# Chemical Calculations

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• Chemical Calculations
• Number of moles in a..
• ...solution
• moles = volume x concentration
• ...compound
• moles = m*** ÷  Mr
• ...gas
• moles = volume ÷ 24dm (molar m***)
• Energetics
• delta H = Hproducts - Hreactants
• Hess's Law delta H1 = delta H2 + delta H3
• delta H = sum of delta H (products) - sum of delta H (reactants)
• mcAT [÷ n] = delta H (J[permol])
• delta H = sum of broken bonds - sum of bonds formed
• products obtained
• percentage yield = 100 x (m*** of product obtained ÷ maximum theoretical m***)
• atom economy = 100 x (m*** of required product ÷ total m*** of reactants)
• Other
• Emission and Absorption Spectra
• c = freq x wavelength
• E=hf
• f proportional to 1/wavelength
• Relative atomic m*** (from m*** spec) = sum of (relative percantage abundance x charge/m*** ratio) ÷ sum of relative percentage abundance
• Empircal formula = E(lement) M(***) A(r) R(atio)
• Kinetics
• rate = change in concentration ÷ time
• delta H = Eaf - Eab