Question

AH= +62.10 k (5 points total) Consider this reaction: 2 Ag,0(s) - 4 Ag(s) + O2(g) 2. How many joules of heat are absorbed when 12.50 milligrams of silver а. oxide is consumed? b. What volume of silver would be produced if 31 megacalories were absorbed in this reaction? The density of silver is 10.5 g/cm

Answer 1

a)

Molar mass of Ag2O,

MM = 2*MM(Ag) + 1*MM(O)

= 2*107.9 + 1*16.0

= 231.8 g/mol

mass(Ag2O)= 12.50 mg

= 0.0125 g

use:

number of mol of Ag2O,

n = mass of Ag2O/molar mass of Ag2O

=(1.25*10^-2 g)/(2.318*10^2 g/mol)

= 5.393*10^-5 mol

Since Δ H is positive, heat is absorbed

when 2 mol of Ag2O reacts, heat absorbed = 62.1 KJ

So,

for 5.393*10^-5 mol of Ag2O, heat absorbed = 5.393*10^-5*62.1/2 KJ

= 1.674*10^-3 KJ

Answer: 1.674*10^-3 KJ

b)

E = 31 M cal

= 31*10^6 cal

= 4.184*31*10^6 J

= 1.297*10^8 J

= 1.297*10^5 KJ

when 62.1 KJ of heat is involved, 4 mol of Ag is reacting

So,

for 1.297*10^5 KJ, mol of Ag = 1.297*10^5*4/62.1 KJ

= 8.354*10^3 mol

Molar mass of Ag = 107.9 g/mol

use:

mass of Ag,

m = number of mol * molar mass

= 8.354*10^3 mol * 1.079*10^2 g/mol

= 9.014*10^5 g

Now use:

Volume = mass / density

= (9.014*10^5 g) / (10.5 g/cm^3)

= 8.58*10^4 cm^3

= 8.58*10^4 mL

Answer: 8.58*10^4 mL