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16 February, 12:38

Milk of magnesia, which is an aqueous suspension of magnesium hydroxide, is used as an antacid in the reaction below. How many molecules of HCl would have to be present to form 70.84 g of MgCl₂? Mg (OH) ₂ (s) + 2 HCl (aq) → 2 H₂O (l) + MgCl₂ (aq)

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  1. 16 February, 12:43
    0
    We need 8.96*10^23 molecules HCl

    Explanation:

    Step 1: Data given

    Mass of MgCl2 = 70.84 grams

    Molar mass of MgCl2 = 95.211 g/mol

    Number of Avogadro = 6.022 * 10^23 / mol

    Step 2: The balanced equation

    Mg (OH) ₂ (s) + 2 HCl (aq) → 2 H₂O (l) + MgCl₂ (aq)

    Step 3: Calculate moles MgCl2

    Moles MgCl2 = mass MgCl2 / molar mass MgCl2

    Moles MgCl2 = 70.84 grams / 95.211 g/mol

    Moles MgCl2 = 0.744 moles

    Step 4: Calculate moles HCl

    For 2 moles H2O and 1 mol MgCl2 produced, we need 1 mol Mg (OH) 2 and 2 moles HCl

    For 0.744 moles MgCl2 we need 2*0.744 = 1.488 moles HCl

    Step 5: Calculate molecules

    Molecules = 1.488 moles * 6.022 * 10^23 / mol

    Molecules = 8.96*10^23 molecules

    We need 8.96*10^23 molecules HCl
  2. 16 February, 12:53
    0
    8.96*10²³ molecules of HCl are needed

    Explanation:

    We analyse the reaction:

    Mg (OH) ₂ (s) + 2 HCl (aq) → 2 H₂O (l) + MgCl₂ (aq)

    1 mol of magnessium hydroxide reacts with 2 moles of hydrochloric acid to produce 2 moles of water and 1 mol of magnessium chloride.

    We determine the moles of salt, to know how many moles of it we have formed. → 70.84 g. 1 mol / 95.2g = 0.744 moles

    Ratio is 2:1, so let's make a rule of three:

    1 mol of chloride can be produced by 2 moles of HCl

    Then, 0.744 of chloride were produced by (0.744 m. 2 m) / 1 m = 1.48 moles of HCl

    Let's find out the number of molecules.

    1.48 moles. 6.02*10²³ molecules / 1 mol = 8.96*10²³ molecules of HCl are needed
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