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Baton rouge community college chem-1121 E
Experiment title:
Experiment 1: Significant digits Dry Lab
Course/Section #:
Chemistry 1121
Semester:
Spring 20 24
ABSTRACT:
In this lab we will learn and practice mathematics in general chemistry. We will learn about
significant figures and how to round off number up to certain significant numbers.
Chemicals:
N/A. It is a dry Lab.
Chemical Reactions:
N/A. It is a dry Lab.
Procedure:
This experiment is a dry lab on Significant digits. Different problems are worked out in Data
analysis.
Apparatus:
N/A. It is a dry lab on mathematics in general chemistry.
DATA/ANALYSIS:
I. Problems
1. If milk is $2.12 per half gallon, eggs are $0.85 per doz, flour is $1.95 for 5lb, sugar is
$2.05 for 5lb and shortening is $3.35 for 3lb, what would be the cost of the ingredients
for the following cake recipe: lpt (2 cup) milk, 4 eggs, 2lb (4 cups) flour, 1lb (2 cup)
sugar, 1lb shortening.
Solution :
Half gallon = 8 cups
Then for two cups price would be = ($2.12 / 8) × 2= $0.
4 eggs price = ($0.85/12) × 4 = $0.
2lb flour price = ($1.95/5lb) × 2lb = $0.
1lb sugar price = ($2.05/5lb) × 1lb = $0.
Shortening price = ($3.35 / 3lb) ×1lb = $1.
Now calculating all amount = $0.53 +$0.28+$0.78+$0.41+$1.
Cost for cake ingredients = $3.
2. If you mixed 8.0 tons of sand, 12 tons of rock, and 4.0 tons of cement to make concrete,
what would the % by weight of sand be?
Solution:
Percentage by weight of sand = (weight of sand/ total weight of mixture) × 100
= (8.0 tons / 8.0 tons+4.0 tons + 12 tons) × 100
= (8.0 tons / 24 tons) × 100
3. If you have a mixture of 10 lb. sunflower seeds which cost 32 cents per pound and 16
lb. of cracked corn which cost 18 cents per pound, how much would this mixture cost
per pound?
Solution:
Cost of 10 lb sunflower seeds = (32cents / 1 lb) × 10lb = 320 cents
Cost of 16 lb cracked corn = 18 cents × 16lb / 1lb = 288cents
total weight of mixture 10 lb + 16lb = 26lb
Total cost = 320 cents + 288 cents = 608 cents
Mass = 297326.4 gm
II. Problems
1. How many significant figures are in these numbers?
a. 0.000090 lb = 2
b. 5 × 10
3
inches = 1
c. 8.09 × 10
5
d. 0.07052 gm = 4
e. 9650000 Coulombs = 3
f. 5.30 cm = 3
2. Solve problems and give correct number of significant figures:
1. 3.14 × 7.506 = 23.
- 1 2.6 gm + 24.30 gm + 0.03621 gm = 36.9 gm
3. 6.4 × 8.741 = 56
III. Problems
Express the numbers and answers as exponential numbers and indicate the number of
significant numbers in the answers.
1. 53107 = 5.3107×
4
, 5 significant figures
2. (7.31×
2
) + (4.2×
3
) − (5.1×
2
)= 4.4 × 10
3
, 2 significant figures
Aligning the exponential numbers = (0.731×
3
) + (4.2×
3
) − (0.51×
3
)
= 4.4 × 10
3
3. 0.00302= 3.02 × 10
, 3 Significant figures
4. 95.30= 9.530 × 10
1
, 4 significant figures
5. 0479×0.7132= 3.4 2 × 10
2
, 3 significant figures
6. 830= 8.3 × 10
2
, 2 significant figures
7. 0.0913×84.31= 7.70 × 10
0
, 3 significant figures
8. 6.00×6.00= 3.60 × 10
1
, 3 significant figures
9. 9.53×
4
÷ 7.2×
2
= 1.3 × 10
2
, 2 significant figures
IV. Problems
1. 3x + 5 = x - 3 solve for x
3x-x = - 3 - 5
2x = - 8
X = - 8/
X= - 4
2. 5x/2 = 3x- 10 solve for x
5x = (3x-10) × 2
5x = 6x - 20
6x - 5x =
4x =
x = 20/
x= 5
3. A/B = y/x solve for y
y=(A/B) ×x
4. A = π (d/2)
2
solve for d
A/ π = (d/2)
2
Taking under root on both sides
Mass = 96.18g
b. The mass in grams of 6.022 × 10
23
molecules or a mole of sulfur dioxide (SO 2 ) is [32.
g + (2x__g)] or __ grams?
6.022 × 10
23
molecules = 1 mole
Molecular mass of sulfur dioxide = 32.06 + 2(16)
= 64.06 g/mol
Moles = mass / molar mass
Mass = moles × molar mass
Mass = 1mol ×64.06 g/mol
Mass = 64.06g
V. Sterling silver contains 92.5% silver and 7.5% copper. A sterling silver dish
weighs 185.0 g. What mass of copper is in the dish?
Percentage of copper = (mass of copper / total mass) × 100%
Mass of copper = (percentage of copper × total mass)/ 100 %
= 7.5% ×185.0g /100%
Mass of copper in dish = 13.88 g
CONCLUSION:
In this dry lab we learned the use of mathematics especially significant numbers. We learned about
solving mathematical problems using unit factor method, how to identify significant numbers and
how to solve addition, subtraction, multiplication and division problems and round off answers up
to certain significant figures.
