A solution has a pH of 2.5. What is its [OH-] ?
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Answer:
( Naphthalene )
Explanation:
Given that:
4.50 g of a Compound X is made up of Carbon , Hydron and Oxygen
It's molecular molar mass = 128 g/mol
Compound X undergoes combustion reaction and the product yield :
CO_2 with mass 15.47g and :
H_2O with mass 2.53 g
The objective is to use this information to determine the molecular formula of X.
We all know that ; number of moles = mass/molar mass
where the molar mass of H_2O is 18 g/mol
number of moles of H_2O product = 2.53 g/18 g/mol
number of moles of H_2O product = 0.1406 moles
Also; the molar mass of CO_2 product = 44 g/mol
number of moles of CO_2 product = 15.47g/ 44 g/mol
number of moles of CO_2 product = 0.3516 moles
number of moles of Compound X in the reactant side= 4.50 g /128 g/mol
number of moles of Compound X n the reactant side= 0.03516 moles
Now; number number of moles of CO_2 in reactant = 0.3516 moles/0.03516 moles
Now; number number of moles of CO_2 in reactant = 10
number of moles of H_2O reactant = 0.1406 moles × 2/0.03516
number of moles of H_2O reactant = 7.997 ≅ 8
Since we said the Compound X is known to be made of Carbon C , Hydrogen H and Oxygen O
Then the molecular formula can be written as :
In order to find the x; we have
128 = (12 × 10 + 1 × 8 + 16 × x)
128 = 120 + 8 + 16x)
128 = 128 + 16 x
128 - 128 = 16 x
0 = 16 x
x = 0/16
x = 0
As x = 0 ; hence there are no oxygen present in the reaction
Thus; the molecular formula of Compound X = which is also known as Naphthalene