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Linda 發問於 科學及數學化學 · 1 十年前

chemistry question

32g of sodium chloride, 32g of tetrachloromethane and 50cm^3 of water are saken together in a stoppered bottle and then allowed to settle. After a few minutes, what would be observed ?

solubility in water at 25degree Celcius (g/100cm^3)

sodium chloride :32


1 個解答

  • 1 十年前

    Two colourless liquid layers are formed. The top layer is water (with greater volume), and the bottom layer is tetrachloromethane (with a smaller volume). A half of the sodium chloride is dissolved in water, but another half sinks in the bottom of the tetrachloromethane layer.

    Reasons :

    - Water and tetrachloromethane are immiscible (do not mix). Both of them are colourless. Therefore, they form two colourless liquid layers with the aqueous layer on the top, since (density of tetrachloromethane) > (density of water) = 1 g mol-1.

    - Volume of water = 50 cm3. Volume of tetrachloromethane = 32/(density of tetrachlormethane) < 32 cm3. Therefore, the aqueous layer has a greater volume than the tetrachloromethane layer.

    - Sodium chloride is soluble in water, but insoluble in tetrachloromethane. Only 16 g (32/2 g) of NaCl is dissolved in 50 cm3 of water, and thus 32-16 = 16 g is not dissolved.

    - Since sodium chloride has a greater density than tetrachloromethane, the undissolved NaCl sinks in the tetrachloromethane layer.