Experiment #1: Hydrates Purpose: Determine the formula of a hydrate ...
Experiment #1: Hydrates Purpose: Determine the formula of a hydrate. (Seeing how scientists even come up with a formula) Hydrate – a salt that is chemically combined with a certain number of water molecules. Typical formula: MB(xH2O) M = metal ion (such as Cu2+) B = counter ion (such as SO42) x = number of moles of water per mole of salt Need to determine what x is in hydrates. Lab Info Work in pairs. Don’t remove glasses until out of the room. Set up a 600mL beaker as a slop jar for collecting chemical waste including water used to wash down other objects. Empty the full slop jar into waste container under the hood. I. A. Quantitative analysis Wash crucible with soap and water (CAPTURE ALL WASHES IN SLOP JAR) [crucible WILL be dirty] set up apparatus for heating crucible tripod with triangle on top crucible into triangle plug in hose for Bunsen burner turn on gas use sparker to light burner adjust rich to lean ratio to get BLUE flame heat crucible for 5 minutes turn off gas, remove Bunsen burner cool crucible for 5 minutes use tongs to pick up crucible into a clean beaker take notebook and weigh crucible to two decimals REPEAT UNTIL MASS CHANGES BY 0.05g OR LESS Use the lowest weight as the actual weight of the crucible I. B. [DO II WHILE I IS GOING ON] Place 0.752.5 g hydrate in crucible using spatula record ID of hydrate weigh crucible and hydrate to two decimals heat until dehydration is complete (steam disappears, color may change) DO NOT OVERHEAT, will only take 13 minutes cool for 5 minutes
weigh to 2 decimals repeat I.A. and I.B. but use a significantly different mass of the same hydrate I. C. find 4 other groups that dehydrated the same hydrate share and exchange data 2 masses of hydrate 2 masses of salt ***if you can’t get data, look on bulletin board on blackboard II. Qualitative Analysis get 3 big test tubes in separate tubes, place 1 cm depth of… copper sulfate (CuSO4) hydrate nickel sulfate (NiSO4) hydrate cobalt chloride (CoCl2) hydrate record appearance heat each test tube for 12 minutes use test tube holder aim away from people at an angle to heat, move test tube in and out of the flame and in circles record observations in notebook cool add a few drops of water record observations Data Analysis Sample data: MO2S5 x H2O MO2S5 = 352 g/mol H2O = 18 g/mol Before heat Weight of crucible= 35.71 g Weight of crucible and hydrate = 37.02 g Weight of hydrate = 1.31 g After heat Crucible and salt = 36.85 g Salt = 1.14 g = 3.24 x 103 mol H2O lost = 0.17 g = 9.43 x 103 mol *share bolded
Graph: On xaxis, mol of salt left On yaxis mol of H2O lost plot your data and shared data using formulas in appendix a of lab manual, calculate linear leastsquares line (best straight line that can be drawn through points of data) slope of line = mol water/mol salt = x Reporting: calculate slope, yintercept, error slope Ex. m = 3.2 +/ 0.4 MO2S5 x 3H2O
weigh to 2 decimals repeat I.A. and I.B. but use a significantly different mass of the same hydrate I. C. find 4 other groups that dehydrated the same hydrate share and exchange data 2 masses of hydrate 2 masses of salt ***if you can’t get data, look on bulletin board on blackboard II. Qualitative Analysis get 3 big test tubes in separate tubes, place 1 cm depth of… copper sulfate (CuSO4) hydrate nickel sulfate (NiSO4) hydrate cobalt chloride (CoCl2) hydrate record appearance heat each test tube for 12 minutes use test tube holder aim away from people at an angle to heat, move test tube in and out of the flame and in circles record observations in notebook cool add a few drops of water record observations Data Analysis Sample data: MO2S5 x H2O MO2S5 = 352 g/mol H2O = 18 g/mol Before heat Weight of crucible= 35.71 g Weight of crucible and hydrate = 37.02 g Weight of hydrate = 1.31 g After heat Crucible and salt = 36.85 g Salt = 1.14 g = 3.24 x 103 mol H2O lost = 0.17 g = 9.43 x 103 mol *share bolded
Graph: On xaxis, mol of salt left On yaxis mol of H2O lost plot your data and shared data using formulas in appendix a of lab manual, calculate linear leastsquares line (best straight line that can be drawn through points of data) slope of line = mol water/mol salt = x Reporting: calculate slope, yintercept, error slope Ex. m = 3.2 +/ 0.4 MO2S5 x 3H2O
