Question 1

If we mixed 45cm^3 of 2m NaOH with 20cm^3 of 1m HCL and obtained a temperature difference of 9.4°C, what would be the heat of reaction, the enthalpy?.

Question 2

If we added 10cm^3 HCL of an unknown concentration to 30cm^3 of 2M NaOH and obtained a temperature change of 4.5°C and then added 20cm^3 of the same unknown acid to 30cm^3 of 2M NaOH and obtained a temperature change of 9.0°C, what is the concentration of the acid? Use the enthalpy value from question 1

1

The heat of reaction is

The enthalpy is

2

The concentration of HCl is  

Explanation:

From the question we are told that

      The volume of   is  

       The number of concentration of   is  

       The volume of  HCl is

        The number of concentration of   is  

        The temperature difference is

Now the heat of reaction is mathematically represented as

Where

      is the specific heat of water with value  

Now  

where   is the molar mass of NaOH  with the value of  0.04 kg/mol

    So    

While  

Where is the molar mass of with the value of  0.03646 kg/mol

So

=>  

The enthalpy is mathematically represented as

=>    

From the second question we are told that

      The volume of  HCl is

       The volume of  NaOH  is  

      The concentration of NaOH is  

       The first temperature change is  

       The second volume of  

The mass of NaOH is

substituting values

The mass of the product formed is

substituting values  

The multiplication by 1000 is to convert it from kg to grams

Now the mass of HCl is  

substituting values    

Now the concentration of HCl is  

The multiplication of is to convert it from kg/mol to g/mol