Which two forces are always equal and opposite for an object on a surface?

Suppose any object with mass in our planet.

The object will be affected by the gravitational force, that pulls the object down. Now, a table in your dining room is also affected by this force, but the table is in a surface (the ground) and it does not move.

We know that if an object does not move, then the net force acting on it is equal to zero, this means that there is a force equal and opposite ot the gravitational force.

This force is the normal force, that the ground applies on the table. This force comes as a "response" to the table pushing the ground (By 3rd Newton's law).

So two forces that are always equal and opposite are the forces caused by this law.

  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

no simpler subs form complex ones. synthesise = make