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6 September, 11:39

How many grams of CaH2CaH2 are needed to generate 147 LL of H2H2 gas if the pressure of H2H2 is 823 torrtorr at 21 ∘C∘C? Express your answer using three significant figures.

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  1. 6 September, 15:30
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    139 g of CaH₂ were needed in the reaction

    Explanation:

    Determine the reaction:

    CaH₂ + 2H₂O → Ca (OH) ₂ + 2H₂

    1 mol of calcium hidride reacts with 2 moles of water to produce 1 mol of calcium hydroxide and 2 moles of hydrogen

    Let's determine the moles of formed hydrogen by the Ideal Gases Law

    P. V = n. R. T

    P = 823 Torr. 1 atm/760 Torr = 1.08 atm

    T = Absolute T° → T°C + 273 → 21°C + 273 = 294K

    1.08 atm. 147 L = n. 0.082. 294K

    (1.08 atm. 147 L) / (0.082. 294K) = n → 6.60 moles

    Ratio is 2:1. We make a rule of three:

    2 moles of H₂ came from 1 mol of hydride

    Then 6.60 moles of H₂ must came from 3.30 moles of hydride (6.60.1) / 2

    Let's convert the moles to mass → 3.30 mol. 42.08 g / 1 mol =

    138.8 g ≅ 139 g
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