Questions 1. Show that heating to removo 20 to 24% oft chloride dihydrate should

Question

Questions 1. Show that heating to removo 20 to 24% oft chloride dihydrate should leave a sample that is close to anhydrous what % of magnesam sulate heptahydrate MgSO,? the mass of a sample of calcium Approximately must be removed to produce you 2. For the commercial hot pack made from 25 g calcium chloride and 117 ml water comment on the magnitude of temperature increase that occurs upon doubling the mass of CaCh while using the same amount of water. Would you expect the increase to be exactly doubled? Explain. emp. emp. 25 24 51 50 23 3. Why would NaOH be a poor choice for use in commercial hot packs? 182 Heat of Solution and Hot Packs

Explanation / Answer

calcium chloride dihydrate (CaCl2.2H2O) ,molecular weight=147.02 u

molecular weight of a molecule of water=18.01 u

To make a molecule of calcium chloride dihydrate as anhydrous calcium chloride ,two molecules of water needs to be removed.

Mass of water to be removed=2*18.01u=36.02 u

% of mass to be removed=(mass removed/mass of calcium chloride dihydrate)*100=(36.02/147.02)*100=24.5%

Thus 24.5% of the mass needs to be removed by heating to form anhydrous calcium chloride

part 2

molecular weight of magnesium sulfate heptahydrate(MgSO4.7H2O)=246.466 u

Mass of water to be removed=7*18.01u=126.07 u

% of mass to be removed=(mass removed/mass of magnesium sulfate heptahydrate)*100=(126.07/246.466)*100=51.1%

Thus 51.1% of the mass needs to be removed by heating to form anhydrous magnesium sulfate heptahydrate

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