There are free body diagrams in the picture, number (#). which of the diagram(s) shows an object at rest on a table? 2 and 3 3 only 2 and 4 2 only

Only #2 represents an object at rest on a table.

In #1, there is no normal force due to the table; the object is accelerating downward.

In #3, the vertical forces are not balanced; the object is accelerating downward.

In #4, neither the vertical nor the horizontal forces are balanced. The object is accelerating upwards AND to the right.

  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