The Nuts and Bolts of Chemistry: Molar Mass and Empirical Formula

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The Nuts and Bolts of Chemistry
Atoms of different elements combine in simple, whole number ratios to form chemical compounds. The
same two elements may combine in different ratios to form various compounds. We will use nuts and
bolts to practice the math involved in this chemical concept.
I. Determine the following masses:
a. Mass of bolt (Bt) = __________
d. Mass of BtNt2 = ___________
b. Mass of nut (Nt) = __________
e. Mass of Bt2Nt = __________
c. Mass of BtNt = __________
II. Compose your own compound and record its mass:
f. Mass of BtxNty = __________
Your compound ____________
III. Find the % Bt and % Nt for each of the compounds.
BtNt
BtNt2
Bt2Nt
BtxNty
% Bt
% Nt
IV. Calculate the empirical formula for each of the compounds by taking the % of one element and
dividing it by the mass of that element. Repeat this calculation with the other element. Divide the
smallest of the two resulting numbers into the larger number. The resulting ratio is the empirical formula.
BtNt
BtNt2
Bt2Nt
BtxNty
Empirical formula
V. Questions
a. Using your measured masses, calculate the composition of Bt2Nt2. Compare it with the %
composition of BtNt. assuming you can’t see the true combination of bolts and nuts what
information could you use to determine what your compound was?
b. Obtain the % composition of BtxNty from another lab group. Calculate the empirical formula of
their compound and see if it agrees.
c. Determine the empirical formula for the following compounds:
i.
H = 6.0%, S = 94.0%
ii.
Na = 21.7%, Cl = 33%, O = 45%
d. What is the empirical formula for 2.3g of Na, 1.2g of C, and 1.6g of O?
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