The emissivity of tungsten is 0.400. a tungsten sphere with a radius of 1.45 cm is suspended within a large evacuated enclosure whose walls are at 320 k. what power input is required to maintain the sphere at a temperature of 3000 k if heat conduction along the supports is negligible?

4850.62 Watt

Explanation:

e = 0.4

radius, r = 1.45 cm = 0.0145 m

To = 320 K

T = 3000 k

According to the Stefan's Boltzmann law

Energy radiated per unit time is given by

where, σ is the Stefan's constant, A be the area of sphere and e be the emmisivity.

So, Power radiated is energy radiated per second

E = 4850.62 Watt

  the grams     of oxygen gas   that can be produced     is 20.6   grams of o₂

calculation

2liclo₃ →   2 licl + 3 o₂

step 1:   find the moles of liclo₃

moles = mass÷ molar mass

from periodic table the molar mass of liclo₃ =6.9 +35.5   +(16 x3) =90.4 g/mol

moles=38.7 g÷90.4 g/mol=0.4281   moles

step 2:   use the   mole ratio   to calculate the moles of o2

from equation above, liclo₃: o₂   is 2: 3  

therefore the moles of   o₂=0.4281 moles x3/2 =0.6422   moles

step 3: find mass   of o₂

mass= moles x molar mass

from periodic table the   molar mass of   o₂ = 16 x2= 32 g/mol

mass=0.6422   moles   x   32 g/mol = 20.6 grams of o₂