How does the magnitude of the lever arm will change if you decrease the angle?

it decreases.
it stays the same.
it increases.

It decreases.

Explanation:

Lever arm is defined as the "perpendicular distance that exists from the rotation axis to the line of action of the force". Being its magnitude related to the application of the force that produces a torque.  

To understand it better:  

The lever arm is an effective distance to apply a force with respect to a certain point, and this distance serves as an effective applied force amplification factor.

In this sense, Torque is defined as:

Where:

is the distance from the applied force to the fulcrum

is the applied force

is the angle between and

It is important to note, is maximum when . Then, assuming and remains the same, if decreases decreases, as well.

Hence:

If the angle decreases, the magnitude of the lever arm will decrease.

So, the greater the lever arm, the greater the torque and the lesser the force we have to apply.

  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

come closer and become far apart and become steam/gas