When 0.945 g of CaO is added to 200.0 mL of 0.500 M HCl(aq), a temperature increase of 387C is observed.
Assume the solution's final volume is 200.0 mL, the density is 1.00 g/mL, and the heat capacity is 4.184 J/gC.
(Note: Pay attention to significant figures. Do not round until the final answer.)
Hrxn, for the reaction of
CaO(s) + 2H+(aq) Ca2+(aq) + H2O(l)
mass water x specific heat water x delta T gives you q.
q/0.945 gives J/g. Multiply by atomic mass to gt J/mol and divide by 1000 to convert to kJ/mol. I wonder about the problem, however. Since this is an aqueous solution, I wonder how the temperature can go to over 100 C. IF it does (forming steam and the steam is heated the remainder of the way, then the above formula will not give the correct answer).
can you plug in the numbers cuz i keep getting it wrong
To calculate the enthalpy change of the reaction, Hrxn, we need to use the equation:
Hrxn = q / n
Where q is the heat transfer in joules (J), and n is the number of moles of the limiting reactant.
First, let's calculate the moles of CaO added:
mass = 0.945 g (given)
molar mass of CaO = 56.08 g/mol
moles of CaO = mass / molar mass = 0.945 g / 56.08 g/mol
Next, let's calculate the moles of HCl in the reaction:
volume of HCl = 200.0 mL (given)
concentration of HCl = 0.500 M (given)
moles of HCl = volume of HCl (in L) * concentration of HCl
To convert mL to L, divide by 1000:
moles of HCl = (200.0 mL / 1000 mL/L) * 0.500 M
Since the balanced equation shows that the ratio of CaO to HCl is 1:2, we can see that the limiting reactant is CaO. Therefore, the number of moles of CaO we calculated earlier will be our value for 'n'.
Now, we need to calculate the heat transfer, q, in joules.
q = mass of solution * specific heat capacity * temperature change
mass of solution = density * volume
density = 1.00 g/mL (given)
volume of solution = 200.0 mL (given)
mass of solution = 1.00 g/mL * 200.0 mL
temperature change = 387C (given)
specific heat capacity = 4.184 J/gC (given)
Now that we have all the values, we can substitute them into our equation for q:
q = (mass of solution) * (specific heat capacity) * (temperature change)
Finally, we can calculate the enthalpy change, Hrxn:
Hrxn = q / n
By substituting the calculated values for q and n into this equation, we can find the value of Hrxn for the given reaction.