The concentration of the solution was determined to be 0.0366 M. Problem #5a: A solution was made by dissolving 52.0 g of hydrated sodium carbonate in water and making it up to 5.00 dm 3 of solution. The standards for being in agreement might vary from one instructor to the next, so make sure to consult with your lab teacher on this point. In some cases, where an extra amount of care must be taken, you would want three straight weighings that were in agreement.Īlso, weighs being in agreement does not mean that they are exactly the same. If the two weights disagree, you continue heating and weighing until you gets weights that agree. If the two weights are in agreement, then you are done heating. H 2O -> 0.43 g / 18.015 g/mol = 0.0239 molĬoCl 2 -> 0.01194 mol / 0.01194 mol = 1ĥ) How can you make sure that all of the water of hydration has been removed?Īfter weighing the anhydrous CoCl 2, you would continue to heat it. What is the formula for the original hydrate? How can you make sure that all of the water of hydration has been removed?Ģ) Determine moles of anhydrous CoCl 2 and H 2O:ĬoCl 2 -> 1.55 g / 129.839 g/mol = 0.01194 mol When cooled, the mass of the remaining dehydrated compound is found to be 1.55 g. Problem #4: A 1.98 g sample of a cobalt(II) chloride hydrate is heated over a burner. What is the value of n in the hydrate's formula?ġ) Calculate moles of anhydrous barium chloride: After heating, 4.26 g of anhydrous barium chloride, BaCl 2, remains.
nH 2O, is heated to drive off the water.Problem #3: A 5.00 g sample of hydrated barium chloride, BaCl 2 The answers will not be exact but enough to tell the formula: What is the empirical formula?ġ) Assume 100 g of the compound is present, then find the moles of each:Ģ) Divide the smallest number into the others. Problem #2: A substance was found to have the following percentages by mass: 23% zinc 11% sulfur 22% oxygen 44% water. What hydrate is it?ġ) The amount of water in the hydrate is:Ģ) The moles of anhydrous LiClO 4 and water are: The mass of the hydrated salt obtained was 7.21 g. Care was taken to isolate all the lithium perchlorate as its hydrate. Problem #1: Anhydrous lithium perchlorate (4.78 g) was dissolved in water and re-crystalized. ChemTeam: Determine the formula of a hydrate: ten problemsĭetermine the formula of a hydrate: ten problems Fifteen examples Calculate empirical formula when given mass data Fifteen problems Calculate empirical formula when given percent composition data A list of all the problems Determine identity of an element from a binary formula and a percent composition Mole Table of Contents Determine identity of an element from a binary formula and mass data
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