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19 March, 07:37

A student mixes a 10.0 mL sample of 1.0 M NaOH with a 10.0 mL sample of 1.0 M HCl in a polystyrene container. The temperature of the solutions before mixing was 20 C.

If the final temperature of the mixture is 26 C, what is the experimental value of delta H?

Assume the solution mixture has a specific heat of 4.2 J/gC and a density of 1 g/mL. A. - 50 kJ/molB. - 25 kJ/molC. - 50,000 kJ/molD. - 500 kJ/mol

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  1. 19 March, 08:45
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    The experimental value of ΔH is - 50 kJ/mol

    Explanation:

    Step 1: Data given

    Volume of 1.0 M NaOH = 10.0 mL = 0.01 L

    Volume of 1.0 M HCl = 10.0 mL = 0.01 L

    Temperature before mixing = 20 °C

    Final temperature = 26 °C

    Specific heat of solution = 4.2 J/g°C

    Density = 1g/mL

    Step 2: Calculate q

    q = m*c*ΔT

    ⇒ with m = the mass

    ⇒ 20.0 mL * 1g/mL = 20 grams

    ⇒ c = specific heat of solution = 4.2 J/g°C

    ⇒ ΔT = T2 - T1 = 26 - 20 = 6 °C

    q = 20g * 4.2 J/g°C * 6°C

    q = 504 J

    ΔHrxn = - q (because it's an exothermic reaction)

    ΔHrxn = - 504 J

    Step 3: Calculate number of moles

    Moles = Molarity * volume

    Moles = 1M * 0.01 L = 0.01 moles

    Step 4: Calculate the experimental value of ΔH

    ΔHrxn = - 504 / 0.01 mol = - 50400 J/mol = - 50.4 kJ/mol

    The experimental value of ΔH is - 50 kJ/mol
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