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Chemistry Percent and Formulas
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Chemistry Percent and Formulas
Chemistry Percent and Formulas
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1
Question
What does the term percent mean in chemistry?
Page 1
Answer
Parts per hundred.
2
Question
What is percent composition of a compound?
Page 1
Answer
The percentage by mass of each element in a compound.
3
Question
In the basic steps for calculating percent using the pizza example, what is step 1?
Page 1
Answer
Write the fraction where the numerator is the part taken and the denominator is the total parts.
4
Question
In the pizza example for percent calculation, what is step 2 after writing the fraction?
Page 1
Answer
Convert the fraction to a decimal, for example 1 ÷ 7 = 0.142857.
5
Question
What is step 3 in the pizza example for converting to percent?
Page 1
Answer
Convert the decimal to percent by multiplying by 100, such as 0.142857 × 100 = 14.29%.
6
Question
What is the molar mass contribution of carbon in ascorbic acid C₆H₈O₆?
Page 1
Answer
6 × 12.0 = 72.0 g.
7
Question
What are the molar mass contributions for hydrogen and oxygen in ascorbic acid C₆H₈O₆?
Page 1
Answer
Hydrogen: 8 × 1.0 = 8.0 g; Oxygen: 6 × 16.0 = 96.0 g.
8
Question
What is the total molar mass of ascorbic acid C₆H₈O₆?
Page 1
Answer
72 + 8 + 96 = 176 g/mol.
9
Question
What is the percent composition of carbon, hydrogen, and oxygen in ascorbic acid, and how does it check?
Page 1
Answer
Carbon: 40.91%, Hydrogen: 4.55%, Oxygen: 54.55%; Check: 40.91 + 4.55 + 54.55 = 100%.
10
Question
What is the definition of an empirical formula?
Page 1
Answer
The simplest whole-number ratio of atoms in a compound.
11
Question
What is the first step in determining an empirical formula from percent composition?
Page 1
Answer
Assume 100 g of the compound.
12
Question
What is step 2 in empirical formula calculation?
Page 1
Answer
Convert percentages to grams.
13
Question
What is step 3 for finding an empirical formula?
Page 1
Answer
Convert grams to moles.
14
Question
In empirical formula steps, what is done after calculating moles?
Page 1
Answer
Divide by the smallest number of moles.
15
Question
What is the final step in determining an empirical formula?
Page 1
Answer
Round to whole numbers.
16
Question
For a compound with 27.27% C and 72.72% O, how many moles of C assuming 100g?
Page 1
Answer
27.27 ÷ 12 = 2.27 mol.
17
Question
For the compound 27.27% C and 72.72% O, moles of O?
Page 1
Answer
72.72 ÷ 16 = 4.55 mol.
18
Question
What is the empirical formula for a compound with 27.27% C and 72.72% O after dividing moles by the smallest?
Page 1
Answer
C: 2.27 ÷ 2.27 = 1; O: 4.55 ÷ 2.27 = 2; Empirical formula: CO₂.
19
Question
What is a molecular formula?
Page 2
Answer
Actual formula of the compound; it is a multiple of the empirical formula.
20
Question
What is step 1 to find molecular formula given molar mass?
Page 2
Answer
Get empirical formula mass.
21
Question
Step 2 for molecular formula determination?
Page 2
Answer
Divide given molar mass by empirical formula mass.
22
Question
What is step 3 to obtain the molecular formula?
Page 2
Answer
Multiply empirical formula subscripts by the result from step 2.
23
Question
What is the molar mass and composition of Vitamin C in the molecular formula example?
Page 2
Answer
Molar mass = 176 g/mol; Composition: 40.9% C, 4.58% H, 54.2% O.
24
Question
What is the empirical formula and its mass for Vitamin C?
Page 2
Answer
Empirical formula = C₃H₄O₃; EF mass = 88 g/mol.
25
Question
How is the molecular formula of Vitamin C determined from empirical?
Page 2
Answer
176 ÷ 88 = 2; Multiply C₃H₄O₃ subscripts by 2 to get C₆H₈O₆.
26
Question
What is a chemical reaction?
Page 2
Answer
A process where one or more substances are mixed and transformed into new substances with different chemical properties.
27
Question
What happens to bonds during a chemical reaction?
Page 2
Answer
Bonds are broken and new bonds are formed.
28
Question
What is true about original substances after a chemical reaction?
Page 2
Answer
They are changed and cannot be easily returned to their original form.
29
Question
Name three examples of chemical reactions.
Page 2
Answer
Rusting of metal, burning of paper, cooking of food.
30
Question
What are reactants in a chemical equation?
Page 2
Answer
Substances that start the chemical reaction; written on the left side of the equation.