LAB#4 MOLE RATIOS, QUALATATIVE
• The coefficient of each substance is the ratio that
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exists between it and the coefficients of each of
the other substance in the reaction.
The mole is the universal unit of chemical ratio, it
applies to all compounds, elements and phases .
In this reaction, any substance that has no
coefficient in front of it is assumed to have a
coefficient of 1 (as in algebra). The KNO3 has a
coefficient of 2.
Pb(NO3)2(aq) + K2Cr2O7(aq)  PbCr2O7(s)) + 2 KNO3(aq)
EXPERIMENTAL DESIGN
• IN THIS LAB, THE REACTANTS (REAGENTS) ARE SUPPLIED AS
AQUEOUS SOLUTIONS (aq). Each solution has the same
concentration, the same number of particles are present in the same
volume of each solution.
• Because each solution has the same concentration, equal volumes
have equal number of particles: volume ratios are mole ratios.
• The volume ratio (which is the mole ratio) that gives you the most
solid product (height in well) is the real mole ratio. You ARE TRYING
TO PROVE EXPERIMENTALLY WHAT IS KNOWN THEORETICALLY IN
THE BALANCED REACTION GIVEN.
• Use your imagination to diagram the reaction, this is called a
simulation or model (File number 5 on school web -download it).