A block of mass 4 kg rests on a frictionless horizontal surface, what horizontal force is required to accelerate the block at 5 m/s^2 ?

20N

Explanation:

Given parameters:

Mass of the block  = 4kg

Acceleration  = 5m/s²

Unknown:

Horizontal force needed to accelerate the block  = ?

Solution:

According to Newton's second law of motion;

     Force  = mass x acceleration

Now insert the parameters and solve;

        Horizontal force  = 4 x 5  = 20N

  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