Answer:
0.2 mole of H2.
Explanation:
We'll begin by calculating the number of mole in 4.71 g of magnesium (Mg). This can be obtained as follow:
Mass of Mg = 4.71 g
Molar mass of Mg = 24 g/mol
Mole of Mg =?
Mole = mass /Molar mass
Mole of Mg = 4.71 /24
Mole of Mg = 0.2 mole
Next, we shall write the balanced equation for the reaction.
This is illustrated below:
Mg + 2HCl —> MgCl2 + H2
From the balanced equation above,
1 mole of Mg reacted to produce 1 mole of H2.
Finally, we shall determine the number of mole of H2 produced from the reaction. This can be obtained as illustrated below:
From the balanced equation above,
1 mole of Mg reacted to produce 1 mole of H2.
Therefore, 0.2 mole of Mg will also react to produce 0.2 mole of H2.
Thus, 0.2 mole of H2 was obtained from the reaction.
The number of moles of H₂ that can be formed if a 4.71 g sample of Mg reacts with excess HCl is 0.19625 moles
Let's represent the reaction with a chemical equation
Mg + HCl → MgCl₂ + H₂
Mg + 2HCl → MgCl₂ + H₂
HCl is in excess according to the question. This means Mg is the limiting reagent and therefore determine the amount of product.
Therefore,
24 g of Mg gives 2g of H₂
4.71 g of Mg will give ? H₂
cross multiply
mass of H₂ = 4.71 × 2 / 24
mass of H₂ = 9.42 / 24 = 0.3925 g
moles of H₂ = mass / molar mass
moles of H₂ = 0.3925 / 2
moles of H₂ = 0.19625 moles
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