Versus/Versus-A
Lab that Students Don't Dread
In the V e r s u ~ N e n u exprriment s studrnu are issued a sample vial which contains: an unknown mntcrial, a label which gives two furmulas-one of whirh is the rorrert formula of the material (e.g.. 6 M HCI versus 6 M NaOtl. Mn2' versus CG*; (.'I- versus NO1- and a numher whirh rs keyed to a master anzwcr 1st. After rerewing the sample, the studrnr must determine the correct sample cornpasition by observation, and/or simple physical or chemical tests. When the sample is returned another sample is issued and the cycle repeated. We have normally scheduled this experiment after the class has completed the qualitative analysis series of experiments since many test reagents are still freshly prepared and the class has had considerable experience with numerous reactions and close observation of color chanees.. meci~itatesand other Dhenomena. Further. we have found that i f a classical oualitative nnalwi
