The Double Y Diagram
by Richard T. Carman
This is a mnemonic aid for solving a variety of stoichiometric problems in the beginning chemistry class.
In solving problems, one always starts on the left and works to the right. The “known” is the substance for
which a quantity is known. The “unknown” is the substance for which a quantity is to be determined.
Simply begin at the left and perform the indicated mathematical calculations as indicated. This diagram is
initially designed for problems at STP.
Volume of
Known (L)
Mass of
Known (g)
Divide by the
Gram-Atomic or
Gram-Formula
Mass
Divide by
22.4 Liters/
mole
MOLES of
KNOWN
Divide by Avogadro’s
Number
Multiply by the
coefficient of the Unknown and
Divide by the
coefficient of the Known
Volume of
Unknown (L)
Mass of
Unknown (g)
Multiply by the
Gram-Atomic or
Gram-Formula
Mass
Multiply by
22.4 Liters/
mole
MOLES of
UNKNOWN
Multiply by Avogadro’s
Number
6.02 X 1023 particles/mole
6.02 X 1023 particles/mole
Make the necessary adjustments for coefficients
and subscripts
Make the necessary adjustments for coefficients
and subscripts
Number of
Particles of Known
Number of
Particles of Unknown
(atoms or molecules)
(atoms or molecules)