Exp. 6 Quiz Name POC1 Lab Answer all questions to the correct number of signific

Question

Exp. 6 Quiz Name POC1 Lab Answer all questions to the correct number of significant figures. 1. Pre welghed samples of 3 salts were placed on separate watch glasses and allowed to remain exposed to the air for 2 hours. Then the following observations were recorded: Salt 1 - Increase in weight and slightly moist Salt 2- Decrease in weight and powdery Salt 3-Increase in weight and significantly dissolved. For each salt, indicate whether it is a bydrate (has water already) or anhydrous (does not have water), Salt 1 Salt 2 Salt 3 and and and 2. Ahdrated salt, molar mass 19881 g/mol, is 36.26% water. a. How many grams of water are in 100.0 g of the hydrate? b. How many grams of anhydrous salt are in 100.0 g of the hydrate? c. How many moles of the anhydrous salt are in 100.0 g of the hydrate? d. How many moles of water are in 100.0 g of the hydrate? 3. Suppose you were given a sample of hydrated FeCh; the molar mass of anhydrous FeCl, is 126.75 g/mol. You measured the weight of the hydrated sample to be 3.42 g. After heating the hydrate to drive off all the water of hydration, you measured the weight of the anhydrous FeCl; to be 2.19 g. Determine the number of waters of hydration for one formula unit of FeClh, and then write the chemical formula for the hydrated salt. (ie. FeCl, X H:0, determine the X. Round to the nearest whole number of water molecules/mol; the molar mass of water is 18.02 g/mol.)

Explanation / Answer

1. Hygroscopic compounds attract water from the surrounding environment and become moist, this result in increase in volume. Deliquescent absorbs moisture until it is dissolved. However, efflorescent molecule give up water and the weight decreases. Hence,

Salt 1 is anhydrous and hygroscopic.

Salt 2 is hydrated and efflorescent.

Salt 3 is anhydrous and deliquescent.

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