Amover uses 1250 j of energy to move a 25 kg box up an inclined plane to a height of 4 m. what was the mover’s efficiency while moving the box?

0.784

Explanation:

Efficiency is the ratio of energy out over energy in.

We know the energy in was 1250 J.

The energy out is the change in potential energy of the box:

PE = mgh

PE = (25 kg) (9.8 m/s²) (4 m)

PE = 980 J

So the efficiency is:

e = 980 J / 1250 J

e = 0.784

  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