jenny asked in Science & MathematicsChemistry · 9 years ago

# need help in chemistry?

suppose you had a 25g sample of air and 25g of silver. Each sample absorbs 325 J of energy. Which substances has the biggest change in temperature? do calcculations to prove your answer.

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• Anonymous
9 years ago

Specific heat equation for solids and liquids:

Q = c·m·∆T

Where:

c is the specific heat constant of the substance

m is the mass of the substance

∆T is the change in temperature

The value of c for silver is 0.233 J/g•K

Given mass and energy, solve for ∆T

∆T = Q/c·m = 325 J / 0.233 J g-¹ K-¹ · 25 g = 55.79 K --(sig figs)--> 56 K

For air, since the question didn't specify whether we were working with constant volume or constant pressure, we'll just assume constant pressure and go from there.

Molar Specific Heat equation for gases at constant pressure:

Q = n·Cp·∆T

Cp = 20.8 J/mol·K

We'll take the molar mass of air to be 28.97 g/mol (source below). Convert that to moles:

25 g / 28.97 g/mol = 0.863 mol

Solve for ∆T:

∆T = Q / n·Cp = 325 J / 0.863 mol * 20.8 J/mol·K = 18 K

Comparing these 2 values, we see that the silver had a greater temperature change (56 K) than the air (18 K).