M asked in Science & MathematicsChemistry · 8 months ago

Anyone can help me with this chemistry question?

A chalk contain calcium hydroxide,Ca(OH)2. This substance is use to neutralise the acidity of soil. A sample of chalk can neutralise 62.5cm^3 of nitric acid,HNO3 1.6moldm^-3 completely. Calculate the mass of the sample.

Answer given is 3.7g

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  • 8 months ago

    Molar mass of Ca(OH)₂ = (40 + 16×2 + 1×2) g/mol = 74 g/mol

    Ca(OH)₂ + 2HNO₃ → Ca(NO₃)₂ + 2H₂O

    Mole ratio Ca(OH)₂ : HNO₃ = 1 : 2

    Moles of HNO₃ = (1.6 mol dm⁻³) × (62.5/1000 dm³) = 0.1 mol

    Moles of Ca(OH)₂ = (0.1 mol) × (1/2) = 0.05 mol

    Mass of Ca(OH)₂ = (0.05 mol) × (74 g/mol) = 3.7 g

    ====

    OR:

    (1.6 mol dm⁻³ HNO₃) × (62.5/1000 dm³) × (1 mol Ca(OH)₂ / 2 mol HNO₃) × (74 g Ca(OH)₂ / 1 mol Ca(OH)₂)

    = 3.7 g Ca(OH)₂

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