In the laboratory a \"coffee cup\" calorimeter , or constant pressure calorimete
ID: 1083459 • Letter: I
Question
In the laboratory a "coffee cup" calorimeter, or constant pressure calorimeter, is frequently used to determine the specific heat of a solid, or to measure the energy of a solution phase reaction.
A student heats 69.66 grams of platinum to 98.86 °C and then drops it into a cup containing 84.34 grams of water at 21.32 °C. She measures the final temperature to be 23.24 °C.
The heat capacity of the calorimeter (sometimes referred to as the calorimeter constant) was determined in a separate experiment to be 1.67 J/°C.
Assuming that no heat is lost to the surroundings calculate the specific heat of platinum.
In the laboratory a "coffee cup" calorimeter, or constant pressure calorimeter, is frequently used to determine the specific heat of a solid, or to measure the energy of a solution phase reaction.
A student heats 69.66 grams of platinum to 98.86 °C and then drops it into a cup containing 84.34 grams of water at 21.32 °C. She measures the final temperature to be 23.24 °C.
The heat capacity of the calorimeter (sometimes referred to as the calorimeter constant) was determined in a separate experiment to be 1.67 J/°C.
Assuming that no heat is lost to the surroundings calculate the specific heat of platinum.
Explanation / Answer
Solution:- Water temperature is increasing it means water gained energy from the metal.
change in temperature, delta T for water = 23.24 - 21.32 = 1.92 degree C
mass of water = 84.34 g
specific heat of water = 4.184 J/g. degree C
heat gained by water is calculated by using the formula,
q = m c delta T
q = 84.34 g x 4.184 J/g.degree C x 1.92 degree C
q = 677.53 J
heat gained by calorimeter is calculated by using the equation,
q = Cp*delta T
where Cp is the heat capacity of calorimeter.
q = 1.67 J/degree C x 1.92 degree C
q = 3.21 J
Heta lost by metal = - (heat gained by water + heat gained by calorimeter)
heat lost by metal = - (677.53 J + 3.21 J)
heat lost by metal = -680.74 J
delta T for metal = 23.24 - 98.86 = -75.62 degree C
mass of metal, m = 69.66 g
we would use the equation, q = m c delta T to calculate the specific heat of metal.
c = q/m*delta T
c = -680.74 J/(-69.66 g * 75.62 degree C
c = 0.129 J/g.degree C
So, the specific heat of the metal(Pt) is 0.129 J/g. degree C.
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