Given :
A certain compound contains 4.0 g of calcium and 7.1 g of chlorine.
Its relative molecular mass is 111.
To Find :
Its empirical and molecular formulas.
Solution :
Moles of calcium , 
.
Moles of chlorine , 
.
The ratio calcium and chlorine is 1 : 2 .
So , the empirical formula is 
.
Now , molecular mass of is :
So , 
Therefore , the molecular formula is also .
Hence , this is the required solution .
For this item, we need to assume that air behaves like that of an ideal gas. Ideal gases follow the ideal gas law which can be written as follow,
PV = nRT
where P is the pressure,
V is the volume,
n is the number of mols,
R is the universal gas constant, and
T is temperature
In this item, we are to determine first the number of moles, n. We derive the equation,
n = PV /RT
Substitute the given values,
n = (1 atm)(5 x 10³ L) / (0.0821 L.atm/mol.K)(0 + 273.15)
n = 223.08 mols
From the given molar mass, we calculate for the mass of air.
m = (223.08 mols)(28.98 g/mol) = 6464.9 g
<em>ANSWER: 6464.9 g</em>
For machines such as a rake the output force is less than the input force. If the input force of the rake is 10 newtons and the output force is 5 Newtons mechanical advantage is .5
