If it took you 5 seconds to move a rock 15 meters using a force of 150 Newtons, how much power did you need to use? 500 joules/sec
45 joules/sec
4,500 joules
450 joules/sec

Given that:

Time taken = 5 seconds

Distance = 15 meters

Force = 150 Newtons

Power = ?

Recall that power is the rate of work done per unit time

i.e Power = work / time

(since work is a product of force and distance, then

power = (force x distance)/ time

Power = (150 Newtons x 15 m) / 5 s

Power = 2250 / 5

Power = 450 joules per second

  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