# Chemistry Unit 3 Equations

All equations and 2 example questions, bond energy example question not included due to them being large and requiring alot of extra information.

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• Created by: richard
• Created on: 15-05-13 14:28
• Chemistry Unit 3 Equations
• Specific Heat Capacity
• How much energy is needed to increase the temperature of 500 g of lead from 20ºC to 45ºC? The specific heat capacity of lead is 128 J/kg ºC.
• mass of lead = 500/1000 = 0.5kg temperature change = 45-20 = 25c energy needed = 0.5 x 128 x 25 = 1600j or 1.6kj
• E =m x c x t
• m = mass
• c = specific heat capacity
• t = temperature change
• Bond Energy Calculations
• You will be given bond energies for example h-h = 436kj per mole.
• Energychange = sum of bonds broken - sum of bonds made
• Titration Equation
• M1 x V1 divided by N1 = M2 x V2 divided by N2
• E.G. 25.00cm of an unknown strength HCL reacted with 38.90cm of 0.100 mole per cm solution of Na OH calculate the concentration of HCL?
• HCL + NaOH = NaCL +H2O
• So where m1 is unknown v1 = 25.00cm n1 = 1  m2 = 0.100 moles per cm v2 =38.9cm and n2 = 1
• M1 = M2 x V2 x N1 divided by N2 x V1
• M1 = 0.100 x 38.90 x 1 divided by 1 x 25.00
• How much energy is needed to increase the temperature of 500 g of lead from 20ºC to 45ºC? The specific heat capacity of lead is 128 J/kg ºC.
• mass of lead = 500/1000 = 0.5kg temperature change = 45-20 = 25c energy needed = 0.5 x 128 x 25 = 1600j or 1.6kj