Calorimetry

# Weight of hclg of solutionmolar mass of hclmols

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(Weight% of HCl*g of solution)/molar mass of HCl=mols (.1053)(42.55g)=4.48g HCl 4.48g/36.458g=.123mol of HCl 6858.04J/0.123mol=55756J/mol To change units from J to kJ we divide by 1000, which results in a q of approximately 55.8kJ/mol, which has an uncertainty of 0.1. Our q is positive because we were calculating the heat of the surroundings, thus to compare it to the accepted it is the opposite charge. In part B we repeated the same procedure as part A, but instead we used an unknown concentration of HCl Data table 2 shows the experimental data collected during Part B of the experiment Weight of Styrofoam Cup Weight of Cup+HCl Weight of Cup+ HCl+NaOH g of HCl 1.71g 44.64g/mL 93.72g/mL 42.93g Repeating the same calculations as in Part A (shown above) we used the data from data table 2 instead and we calculated ∆T as 19.34 q for part B= 6441.69J This time we were to find the weight % by using an accepted value for J/mol as 55,900J/mol So using x as the value for the weight %* g of HCl the set up would be… 55,900J/mol=6441.69/(x/36.458) 55,900x=234851.134 x=4.2 In order to find the weight % we must set up another equation (weight%*g of HCl)=x Weight % * 42.93=4.2 Weight %= 0.098 or 9.8% Table 3 shows weights gathered before experiment Weight of Styrofoam Cup Weight of Cup+H2O Weight of Cup+H2O+HCl 1.83g 41.35g 56.19g Table 4 shows data analysis gathered throughout the lab that helps with the calculations for Part C Concentration of NaOH Density of NaOH g/mL mL of NaOH needed to completely react with HCl 10.57 (+/-) 0.01 1.0141(+/-) 0.0001 14.0 mL of NaOH

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Both data from table 3 and 4 will be used in the following calculations To find the g of NaOH we use the density and known composistion Density*mL of solution* weight% 1.0141g/mL*14.0mL*.1057=1.5 To find the mols of NaOH we divide by the molar mass 1.5/39.9971=0.0375mol NaOH For the HCl and NaOH reaction the chemical equation is written as HCl+NaOH >H2O+NaCL Using the mol ratio we know the same number of mol of HCl will be used as NaOH thus we use the mol of HCl to find the weight % Mol*molar mass=g of HCl 0.0375mol*36.461g/mol=1.367g of HCl
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