Overall this was a great lab. The background was the only section that I took off points. I
felt that ideas needed to be connected a little better so the paragraph had better flow.
Determination of a Chemical Formula
Purpose –
The objective of this lab is to find the formula of copper chloride hydrate, which has a
general formula of CuxCly zH2O. This will be done by finding the masses of copper,
chlorine, and water in a sample of the substance. The water will be evaporated off and the
chlorine will be filtered out.
Background –
The law of conservation of mass states that the mass before a reaction is the same as the
mass after a reaction. Because of this law, the masses of the components of copper chloride
hydrate can be determined after performing various experiments on the substance. The
composition of a pure substance, regardless of its source, is the same, as stated by the law
of definite proportions. This means the empirical formula is the same for every sample of
copper chloride hydrate. The law of multiple proportions states that elements combine in
small, whole number ratios. This will be helpful in finding the chemical formula of copper
chloride hydrate. A chemical formula is composed of symbols and corresponding
numerical subscripts that give the proportions of the atoms of the elements in a substance.
The empirical formula is the simplest ratio of these atoms. The empirical formula can be
determined by calculating the mole ratio of the substance.
A mole is a unit in chemistry that represents an amount of molecules, ions, or atoms. By
definition, a mole is the number of atoms in 12 grams of 12C. The number of atoms in 12
grams of 12C is approximately 6.02 x 1023 (called Avogadro’s number). The mass of an
element is equal to the number of moles of that element. For example, hydrogen has a
mass of one gram, which is equal to one mole of hydrogen, while, oxygen has a mass of
sixteen grams, which is equal to one mole of oxygen.
This is then used to determine the chemical formula of a substance. First, determine the
masses of the atoms of the elements in the substance, and then convert it to moles. The
ratio of the moles of each atom in the substance is the mole ratio, which is then used to
determine the chemical formula. The mole ratio of the atoms becomes the subscripts that
