1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Coffee Calorimetry Problem

  1. Oct 15, 2011 #1
    1. The problem statement, all variables and given/known data
    The reaction of 0.050 g of solid Mg with 100.0 mL of 1.00M aqueous HCl solution is carried out in a coffe-cup calorimeter. The temperature of the solution increases from 22.21 degrees Celsius to 24.46 degrees Celsius. How much heat is produced by the reaction?

    2. Relevant equations
    Q = m*c*Δt

    Mg + 2HCl → MgCl2 + H2

    3. The attempt at a solution
    mols Mg = .002057
    mols HCl = .1
    Limiting Reactant = Mg
    Δt = 2.25 degrees Celsius

    I am confused since there is no water involved in the reaction. Assumptions I was given are:
    1. The specific heat/molar heat of a calorimeter is small and can be ignored.
    2. The specific heat/molar heat of a dilute aqueous solution is the same as that of water, c = 4.184 J/g°C.
    3. The densities of dilute aqueous solutions are approximately 1.00 g/mL.

    I believe I am to use the Q = mct equation. I know the specific heat, c, should be 4.184, and that the change in temperature is 2.25 degrees Celsius. However, I am not sure what to put for m, the mass. Should m be the total mass of everything or just the mass of the substances actually used in the reaction that takes place?
  2. jcsd
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted