What makes a compound a pure substance ​

Compounds contain more than one type of material. Yet both compounds and elements are considered pure substances. 

Pure compounds are created when elements combine permanently, forming one substance

Extra:

So, a mixture can be separated into its original components, while a pure compound cannot.

weight of any object is given by

w = m*g

where m is mass of the object and g is the acceleration due to gravity.

for earth the value of g is 9.8 m/s^2 so

w=117.6 n m=12 g=?

117.6=12g => g=9.8 m/s^2

which is the force of gravity on earth.