? asked in Science & MathematicsChemistry · 9 years ago

Calculate the Heat Absorbed?

6.84g of NaNO3 are placed into 288g of H2O and the temperature rises 12 degrees Celsius.

Find:

(a) the heat absorbed by the water

(b) the # of mol of salt used

(c) the heat of solution of the salt in J/mol and kJ/mol

Please help, I'm really unsure of what to do.

1 Answer

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  • John
    Lv 6
    9 years ago
    Favorite Answer

    one equation you need is the famous

    Q = m*c*delta T the eenergy is the product of the mass, the temp change, and the specific heat of the material being warmed up.

    so, Q = 288 * 4.18 * 12 = 14446 joules = 14.446 kJ

    one mole of sodium nitrate would have a mass of 85 grams (23 + 14 + 16 + 16 + 16)

    1 gram os sodium nitrate represents one 85th of a mole

    so 6.84 grams is 6.84 85ths of a mole

    Now you need to imagine what the temperature rise would be if you used a mole of sodium nitrate.

    Or better still, what energy would be given out if you dissolved a mole of NaNO3

    To calculate it you need to divide the joules (or kilojoules) by the moles.

    it's all there in the unit of the answer; kilojoules per mole.

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