4. Which of the following statements best describes the relationship between mechanical, kinetic and potential energies of an object of mass
m kg that is thrown vertically upwards with in initial velocity of v. m/s.
A. Kinetic energy increases while potential energy decrease and mechanical
energy remains constant.
B. Kinetic energy decreases, while potential energy increases and mechanical
energy remains constant.
C. Both kinetic and potential energies decrease while mechanical energy
increases.
D. Both kinetic and potential energies increase while mechanical energy
remains constant.
(1)
21

Explanation:

increase while mechanical energy remains constant

  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

80cm/s.

24cm/s.

53.3cm/s.