How many moles of H2 can be formed if a 4.71 g sample of Mg reacts with excess HCl?

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

read more: link

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 equation that correctly represent the reaction for formation of ammonia is

n2+ 3h2 → 2nh3 (answer d)

1 mole of nitrogen gas (n2) react with 3 moles of hydrogen gas (h2) to form 2 moles of ammonia ( nh3). this is in a process known as haber process were iron is used as a catalyst and reaction take place that a higher temperature and pressure. the process is exothermic hence energy is released.

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.