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[tex] Mg(OH)_2(aq) + 2HCl(aq) \rightarrow 2H_2O(l) + MgCl_2(aq) [/tex]

A. How many moles of magnesium hydroxide are required to react with 0.321 moles of hydrochloric acid?

B. What is the molar mass of magnesium hydroxide?

C. What is the molar mass of hydrochloric acid?

D. Given [tex] 6.50 \, g [/tex] of magnesium hydroxide, how many grams of hydrochloric acid are needed to react with that [tex] 6.50 \, g [/tex]?

Sagot :

To address the given problem, we will consider each part separately. Here are the steps:

A. Calculating moles of magnesium hydroxide to react with 0.321 moles of hydrochloric acid

1. Write the balanced chemical equation:
[tex]\[ Mg(OH)_2 + 2 HCl \rightarrow 2 H_2O + MgCl_2 \][/tex]
2. From the equation, we see that 1 mole of [tex]\( Mg(OH)_2 \)[/tex] reacts with 2 moles of [tex]\( HCl \)[/tex].
3. We are given 0.321 moles of [tex]\( HCl \)[/tex].
4. Calculate the moles of [tex]\( Mg(OH)_2 \)[/tex] required using the stoichiometric relationship:
[tex]\[ \text{Moles of } Mg(OH)_2 = \frac{\text{Moles of } HCl}{2} = \frac{0.321}{2} = 0.1605 \][/tex]

B. Calculating the molar mass of magnesium hydroxide

1. The chemical formula of magnesium hydroxide is [tex]\( Mg(OH)_2 \)[/tex].
2. The atomic masses are:
- [tex]\( Mg \)[/tex]: 24.305 g/mol
- [tex]\( O \)[/tex]: 16.00 g/mol
- [tex]\( H \)[/tex]: 1.008 g/mol
3. Calculate the molar mass of [tex]\( Mg(OH)_2 \)[/tex]:
[tex]\[ \text{Molar mass of } Mg(OH)_2 = 24.305 + 2 \times (16.00 + 1.008) = 24.305 + 2 \times 17.008 = 24.305 + 34.016 = 58.321 \text{ g/mol} \][/tex]

C. Calculating the molar mass of hydrochloric acid

1. The chemical formula of hydrochloric acid is [tex]\( HCl \)[/tex].
2. The atomic masses are:
- [tex]\( H \)[/tex]: 1.008 g/mol
- [tex]\( Cl \)[/tex]: 35.453 g/mol
3. Calculate the molar mass of [tex]\( HCl \)[/tex]:
[tex]\[ \text{Molar mass of } HCl = 1.008 + 35.453 = 36.461 \text{ g/mol} \][/tex]

D. Calculating the grams of hydrochloric acid needed to react with 6.50 g of magnesium hydroxide

1. Calculate the moles of [tex]\( Mg(OH)_2 \)[/tex] from its given mass:
[tex]\[ \text{Moles of } Mg(OH)_2 = \frac{\text{Mass of } Mg(OH)_2}{\text{Molar mass of } Mg(OH)_2} = \frac{6.50}{58.321} = 0.1114 \text{ moles} \][/tex]
2. From the balanced equation, 1 mole of [tex]\( Mg(OH)_2 \)[/tex] reacts with 2 moles of [tex]\( HCl \)[/tex]. Therefore, the moles of [tex]\( HCl \)[/tex] required are:
[tex]\[ \text{Moles of } HCl = 0.1114 \times 2 = 0.223 \text{ moles} \][/tex]
3. Calculate the mass of [tex]\( HCl \)[/tex] needed:
[tex]\[ \text{Mass of } HCl = \text{Moles of } HCl \times \text{Molar mass of } HCl = 0.223 \times 36.461 = 8.127 \text{ g} \][/tex]

Hence, the solutions to the respective parts are:

- A. 0.1605 moles of [tex]\( Mg(OH)_2 \)[/tex] are required to react with 0.321 moles of [tex]\( HCl \)[/tex].
- B. The molar mass of [tex]\( Mg(OH)_2 \)[/tex] is 58.321 g/mol.
- C. The molar mass of [tex]\( HCl \)[/tex] is 36.461 g/mol.
- D. To react with 6.50 g of [tex]\( Mg(OH)_2 \)[/tex], you need 8.127 g of [tex]\( HCl \)[/tex].