13th Edition

Instructions are given for the 11th, 12th, and 13th Editions.

You'll find that textbooks will mention names or formulas for substances in their questions but not say what that substance is. You'll find that I want you to look up what they are talking about. Being at the computer, it's easy to do that.

Be sure to go through my online tutorial of "Classifying: Calming the Chaos" first.
I find it interesting that the 11th edition had the same idea I had about chaos. Here is a quote from that textbook. It's the first two sentences of Chapter 3.

"Throughout our lives, we seek to bring order into the chao that surrounds us. To do this we classify things according to similarities."

Chapter 3: Elements and Compounds:
11th Edition, p44-60
12th Edition, , p47-60
13th Edition, , p43-55

Read the whole chapter. Much is covered in my online tutorial, but there are some addition information here.

Percent distribution:
11th Edition, section 3.5, pg 49-51:
12th Edition, section 3.2, pg. 49-50
13th Edition, section 3.2, pg. 45-46

In this section the textbook lists the percent distribution of elements in the universe, Earth's crust, and human body. This is interesting, but they left out a critical piece of information in the 11th and 12th editions. For example, they said hydrogen makes up 10% of the human body. 10% means 10 out of a 100; unfortunately, they didn't say whether this was by weight or by number. In other words, they didn't say if this was 10 atoms of hydrogen out of 100 atoms of the body (by number) or was this 10 grams of hydrogen for every 100 grams (by weight) There's a big difference.
To find out let's visit webelements.com. If you follow this link you will see that they give two numbers for abundance: ppb by weight and ppb by atoms (number of atoms). "ppb" means parts per billion. Remember "%" means parts per hundred.

This is the chart from the webpage. Notice for humans hydrogen is given as 100000000 ppb by weight. That's a fraction of 100 million over 1 billion. That reduces to 1/10, but for percent we need over 100.
 100,000,000  =  1 =  10 = 10%
1,000,000,000   10   100
The textbook said 10% so now we know they meant 10% by weight meaning 10% of the weight of the body is hydrogen. Also, all of their other listings of percent is meant to be by weight. Shame on them for not being more specific. At least in the 13th Edition they corrected that oversight.

Note we are sometimes interested in what fraction of the total number of atoms is hydrogen. Webelements gives that fraction as 620000000 ppb. That's a fraction of 620,000,000 over 1 billion. That reduces to 62/100, which is 62%
 620,000,000  = 62 = 62%
1,000,000,000  100
62% is very different from 10%, so it's extremely important that when % is given in chemistry, one clarifies what are the units. Remember dimensional analysis depends on the units.
Problem 1: What percent of all atoms in the universe are hydrogen atoms?

Problem 2: Chemical formulas :
11th Edition, Question 37, page 62
12th Edition: Question 7, page 62
13th Edition: Not in this edition, but problem is shown below.

Explain the meaning of each symbol and number in these formulas.

(a) H₂O
(b) Na₂SO₄
(c) HC₂H₃O₂

Problem 3: Regarding (b), what is the name for the compound Na₂SO₄? Hint: use search engine and type in Na2SO4.

Regarding (c), when you see "H" written twice, that usually means that the compound is an acid. An acid has one or more hydrogen atoms that get released into water as H⁺. That's what makes it an acid. Those hydrogens that get released are usually written separate from the hydrogens that don't come off.

Problem 4: What acid is HC₂H₃O₂? Hint: use a search engine and type in HC2H3O2 and look for a name of an acid being shown.

Problem 5: Total number of atoms in compound:
11th Edition, Question 39, page 62
12th Edition: Question 9, page 62
13th Edition: Not in this edition, but problem is shown below.

How many (total) atoms are represented in each formula? (just give total atoms for each formula)
a) KF
b) CaCO₃
c) K₂Cr₂O₇
d) NaC₂H₃O₃
e) (NH₄)₂C₂O₄

Problem 6: Regarding (b) CaCO₃. What is the chemical name for CaCO₃? (remember hint before). Also, check out Wikipedia's article on its name and the first paragraph mentions a medicinal use for CaCO₃. What is it medicinal use?

Problem 7: Regarding (d) NaC₂H₃O₂. 7a) What is the chemical name for NaC₂H₃O₂? (a Google search will find it, but I discovered that typing nac2h3o2 into Wikipedia is much easier). 7b) Also, in the Wikipedia's article report one way in how it is made (see Preparation heading).

You should recall in the earlier tutorial titled "Symbols vs. Real" I wanted you to always be aware of what are symbols and what are the real things. A textbook is full of symbols in the form of words, numerals, element symbols, formulas, and many other symbols. The only real elements the textbook can show are carbon, oxygen, and hydrogen with some silicon and aluminum. That's the elements in paper. The compounds in paper are cellulose (long chains of sugar) and clay or chalk. Chapter 3 introduces the symbols of elements and compounds.

Problem 11: What elements are represented in these "words"?
(a) COKEs   (b) CoKEs
(c) TiDy  
(d) KrYPTiC  (e) SnOB

Since words and chemistry both share the same set of symbols, which is the English alphabet, there's a way to write words and at the same time be writing element symbols. This problem was to make you aware of the importance of upper and lower case. In chemistry, that can easily change which element you are representing.

In the sentence shown, it seems that we are reading about Cindy and Nick; however, it's really just symbols for elements. I can see that spies could use this technique to communicate formulas or elements by disguising them as sentences. For example, the formula for the strongest permanent magnet is NdFeB (Neodymium, iron, & boron).
Problem 12: Which words in these sentences have the symbols for these three elements (hint: there are 2 words)?

Problem 13: What elements are listed in the series of element symbols that look like the word "beverages"?