You have a badly tarnished silver teapot. The tarnish is a result of the silver metal reacting with the oxygen in the air according to

4Ag(s) + O2(g) = 2Ag2O(s),
Delta H = -62.2 kJ/mol


You carefully clean the teapot and then, out of curiosity, you weigh it. The teapot has a mass of 877 g. After some more measuring and calculating, you also determine that 6.70 % of the silver is on the surface and exposed to the air.

If the teapot were once again to become completely tarnished, how much mass (Delta m) is converted to energy?

E=mc^2, c= 3*10^8 m/s

877g * .0670 (the percent on surface) = 58.759 * 1molAg/107.9g = .5446 mol Ag

-62.2 kJ/mol /4 (from chem equation) =
15.55 kJ (can lose the negative sign)

-15.55kJ * .5446 mol Ag = -8.46853 kJ *1000J = 8468.53 J
8468.53J = m(3.0x10^8)^2 solve for m

answer will be in Kg so multiply by 1000 to get grams.

I would multiply 877 x 0.067 = g Ag exposed.

Change to moles Ag, use the equation to convert to kJ, then use delta E = delta m*c^2 and calculate delta m. Post your work if you get stuck.

I got stuck.

To determine the mass converted to energy when the teapot becomes tarnished, we can use the equation E=mc^2, where E is the energy, m is the mass converted, and c is the speed of light.

First, we need to calculate the mass of silver that is exposed to the air and available for tarnishing. To do this, we multiply the total mass of the teapot by the percentage of silver that is on the surface and exposed to the air:

Mass of exposed silver = 877 g * 6.70% = 58.709 g

Next, we need to calculate the moles of exposed silver. The molar mass of silver (Ag) is 107.87 g/mol:

Moles of exposed silver = Mass of exposed silver / molar mass of silver
= 58.709 g / 107.87 g/mol
= 0.543 mol

Now, to determine the energy released per mole of tarnished silver, we can use the enthalpy change (ΔH) of the reaction:

Energy released per mole of silver (ΔE) = ΔH / Avogadro's number
= -62.2 kJ/mol / 6.022 x 10^23 mol^-1
= -1.03 x 10^-19 J

Finally, we can calculate the mass converted to energy using the equation E = mc^2:

m = E / c^2
= (-1.03 x 10^-19 J) / (3 x 10^8 m/s)^2
= -3.62 x 10^-35 kg

Since mass can't be negative, we can conclude that 3.62 x 10^-35 kg of mass is converted to energy when the teapot becomes completely tarnished.