The reason why some water and heat are added after Mg ribbon is reacted completely with air is to remove Mg3N2 as MgO.
Combustion reaction is a reaction in which a substance is completely burnt in oxygen. Magnesium ribbon can be converted to magnesium oxide by combustion in air.
The reaction is as follows; 2Mg(s) + O2 ----> 2MgO(s)
Since air contains nitrogen, Mg3N2 is also formed. Heat and water can be added to the reaction thereby converting magnesium nitride to magnesium oxide.
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Answer:
Explanation:
Methanol's molecular weight: 
Methanol's heat of vaporization: 
Ideal gas heat capacity (Cp):
where R is the gas constant
The heat needed to vaporize and bring the gs to 210°C is:
<span>STP means standard temperature
and pressure at 0°C (273K) and 1 atm (atmosphere). The density of the unknown
gas is 0.63 gram per liter. The deal gas equation is PV = nRT. The n is the
numer of moles and can be represented as mass of the gas, m, divided by the
molar mass, c. so we have,</span>
PV = nRT
PV = (m/c)RT
Since the density is d = m/V
Pc = (m/V)RT
Pc = dRT
c = drT/P
substitute the values into the equation,
c = [(0.63g/L)(0.08206
L-atm/mol-K)(273K)]/(1atm)
<u>c = 14.11 g/mol</u>
