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Answer:
1. Percentage by weight = 0.5023 = 50.23 %
2. molar fraction =0.153
Explanation:
We know that
Molar mass of HClO4 = 100.46 g/mol
So the mass of 5 Moles= 5 x 100.46
Mass (m)= 5 x 100.46 = 502.3 g
Lets assume that aqueous solution of HClO4 and the density of solution is equal to density of water.
Given that concentration HClO4 is 5 M it means that it have 5 moles of HClO4 in 1000 ml.
We know that
Mass = density x volume
Mass of 1000 ml solution = 1 x 1000 =1000 ( density = 1 gm/ml)
m'=1000 g
1.
Percentage by weight = 502.3 /1000
Percentage by weight = 0.5023 = 50.23 %
2.
We know that
molar mass of water = 18 g/mol
mass of water in 1000 ml = 1000 - 502.3 g=497.9 g
So moles of water = 497.7 /18 mole
moles of water = 27.65 moles
So molar fraction = 5/(5+27.65)
molar fraction =0.153
<u>Answer:</u> The mass of iron (II) oxide that must be used in the reaction is 30.37
<u>Explanation:</u>
The given chemical reaction follows:

By Stoichiometry of the reaction:
When 635 kJ of energy is released, 6 moles of iron (II) oxide is reacted.
So, when 44.7 kJ of energy is released,
of iron (II) oxide is reacted.
Now, calculating the mass of iron (II) oxide by using the equation:

Moles of iron (II) oxide = 0.423 moles
Molar mass of iron (II) oxide = 71.8 g/mol
Putting values in above equation, we get:

Hence, the mass of iron (II) oxide that must be used in the reaction is 30.37
Answer:
H2 + CaCl2 -> 2HCl + Ca
How many grams of HCl are made when 2.93 g of
Ca are made?
Explanation:
From the given balanced chemical equation, it is clear that:
2mol. of HCl and 1mol. of Ca are produced.
2mol. of HCl weighs --- 73.0g
1mol. of Ca weighs --- 40.0g
Hence,
73.0g of HCl and 40.0g of Ca are produced.
When 2.93g of Ca is produced then, how many grams of HCl will be produced?

Hence, 5.35g of HCl is formed.