CHEM125 – CHAPTER 01 – BASIC HOMEWORK I

CHAPTER 1 BASIC HOMEWORK

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Question 1

CHEM125 - CHAPTER 01 - BASIC HOMEWORK I 1

Measurements are not exact. This is why significant figures are needed. What is the best you can say about the length of the green rectangle? (Feedback is given for each answer)

Select one: chem125-1b - Fluff Butt Reviews

Explanation

This is the best answer. Someone else may say 1.23 or 1.25 cm. These are all good answers and better than 1.2 cm. Widget is loading comments… */ ]]>

Question 2

How many significant figures are in 95.4?

Help: Rules for Significant Figures

chem125-1b - Fluff Butt Reviews

Explanation

  1. All non-zero digits are significant. For example, 1.489 has 4 significant figures.

Question 3

How many significant figures are in 100.0000? chem125-1b - Fluff Butt Reviews

Explanation

  1.  Zeros are significant only when they occur:
  • between two non-zero digits. For example, 309 has 3 sig. fig. and 2,004 has 4 sig. fig.
  • to the right of a decimal point if preceded by a non-zero digit. For example 1.40 and 2.00 have 3 sig. fig. and 0.00170000 has 6 sig. fig. This is easy to tell in scientific notation–1.70000 x 10-3
  • to the left of a decimal if preceded by a non-zero digit. For example, 500. has 3 sig. fig., but 500 has only one.

Question 4

How many significant figures are in 0.00076? chem125-1b - Fluff Butt Reviews

Explanation

Zeros to the left of a number are not significant

Question 5

How many significant figures are in 1.00056? Review: Rules for Significant Figures chem125-1b - Fluff Butt Reviews

Explanation

Zeros are significant only when they occur between two non-zero digits. For example, 309 has 3 sig. fig. and 2,004 has 4 sig. fig.

Question 6

How many significant figures are in 600700000? chem125-1b - Fluff Butt Reviews

Explanation

  • Zeros are significant only when they occur between two non-zero digits. For example, 309 has 3 sig. fig. and 2,004 has 4 sig. fig.
  • To the left of a decimal if preceded by a non-zero digit. For example, 500. has 3 sig. fig., but 500 has only one.

Question 7

How many significant figures are in 44070.? chem125-1b - Fluff Butt Reviews

Explanation

  •  Zeros are significant only when they occur between two non-zero digits. For example, 309 has 3 sig. fig. and 2,004 has 4 sig. fig.
  • To the left of a decimal if preceded by a non-zero digit. For example, 500. has 3 sig. fig., but 500 has only one.

Question 8

Write 329600 in scientific notation to the correct number of significant figures. For example, 136 = 1.36 x 102 . In Moodle write 1.36e2 or 1.36E2. Help: Scientific Notation Exampleschem125-1b - Fluff Butt Reviews

Explanation

In scientific notation it is the number of digits used to write the number, e.g. 1.23 x 103 has 3 significant digits. Its value is 1,230(the decimal is moved 3 places to the right). 1.23 x 104 has 3 significant figures. Its value is 12,300. 1.2300 x 106 has 5 significant figures. Its value is 1,230,000. 1.03 x 10-2 has 3 significant figures. Its value is 0.0103.

Question 9

How many significant figures are in 1.0698 x 104? Review: Scientific Notation Exampleschem125-1b - Fluff Butt Reviews

Explanation

  • Non-zero numbers are significant
  • Zeros are significant only when they occur between two non-zero digits.

Question 10

How many significant figures are in 2.469 x 10-1? chem125-1b - Fluff Butt Reviews

Explanation

  • Non-zero numbers are significant

Question 11

What is 0.0024 in scientific notation? For example, 0.027 = 2.7 x 10-2. In Moodle write 2.7e-2 or 2.7E-2. chem125-1b - Fluff Butt Reviews

Explanation

Moving the decimal to the right makes the nth power negative

Question 12

What is 174.23 rounded to the nearest whole number? Help: Rounding Exampleschem125-1b - Fluff Butt Reviews

Explanation

When rounding, look at the digit to the right of the place you want to round to. If it is 4 or smaller, round down. If it is 5 or greater, round up. Examples: 104.91 rounded to the nearest whole number is 105. 104.91 rounded to the nearest 10, it is 100 or 1.0 x 102. 47.04662 rounded to the nearest hundredth is 47.05. 47.04662 rounded to the nearest tenth is 47.0. 47.04662 rounded to the nearest ten is 50 or 5 x101. 47.04662 rounded to the nearest hundred is 0. When doing calculations, wait until the end before rounding to avoid accumulative round-off error.

Question 13

What is 337.3 rounded to 2 significant figures? chem125-1b - Fluff Butt Reviews

Explanation

47.04662 rounded to the nearest ten is 50

Question 14

What is 60511 rounded to 3 significant figures? chem125-1b - Fluff Butt Reviews

Explanation

Just round to the nearest thousand because nonzero numbers are significant and zeros between nonzero numbers are significant

Question 15

What is 9131.7 rounded to 1 significant figure? chem125-1b - Fluff Butt Reviews

Explanation

Just round the first number on the left based on the number on the right.

Question 16

What is 4.24+ 31 to the correct number of significant figures? Help: Addition and Subtraction Exampleschem125-1b - Fluff Butt Reviews

Explanation

In addition and subtraction, you only know your information to the least accurate decimal place. For example, 2.2 + 15.251 = 17.451 = 17.5 because each number is known to at least the tenth decimal place. Do not use the number of significant figures in addition and subtraction.

Examples: 200 + 468 = 668 = 700 or 7 x 102 2.00 x 102 + 468 = 668 or 6.68 x 102 60 – 4.337 = 55.663 = 60 or 6 x 101 14 +330.4 -0.889 = 343.511 = 344 or 3.44 x 102

Question 17

What is 56.8 – 44.724 to the correct number of significant figures? chem125-1b - Fluff Butt Reviews

Explanation

Least accurate number is 56.8 so round your final answer to the tenths!

Question 18

What is 736.4 +5 – 180.27 to the correct number of significant figures? chem125-1b - Fluff Butt Reviews

Explanation

PEMDAS (#neverforget) 736.4 + 5 = 741.4 (least accurate number is 5) 741.4 – 180.27 = 561.13 ( least accurate number is 741) The final answer is simply 561

Question 19

What is 14 x 301.67 to the correct number of significant figures? Help: Multiplication and Division Exampleschem125-1b - Fluff Butt Reviews

Explanation

In multiplication and division, the correct number of significant figures in the answer is the same as the original number with the fewest. Examples:
12 x 468 = 5,616 = 5,600 or 5.6 x 103
6/207 = 0.0289… = 0.03 or 3 x 10-2
700 x 103 *15 = 1,081,500 = 1,000,000 or 1 x 106. Remember 700 has 1 sig. fig. Specific Answer ( I know this is what you wanted, but kiddos I can’t help ya on the test so you’re gonna have to put some effort in) 14 x 301.67 = 4223.38 ( 14 has the least amount of sig figs; 2)

Question 20

What is 10/21.52 to the correct number of significant figures? chem125-1b - Fluff Butt Reviews

Explanation

Look above! (1 sig fig because 10 only has 1 and according to division and multiplication rules you go by the number with the least amount of sig figs)

Question 21

What is 11.81 x 0.15/984.7 to the correct number of significant figures? chem125-1b - Fluff Butt Reviews

Explanation

  1. Identify order of operations [PEMDAS]
  2. Follow sig fig, rules for the individual operations
  3. Round off at the end. [DO IT FOR ME PLS]
  4. Review the rules before before you begin.
  • Addition/Subtraction rules: Answer must have same # decimal places as the number with the fewest decimals; i. e. the number that is least accurate.
  • Multiplication/Division rules: Answer must have same # sig figs as the number with with the lowest # of sig figs.

PS: YOUR FINAL ANSWER CANNOT BE MORE ACCURATE THAN THE LEAST ACCURATE NUMBER IN THE EQN.!!!

Example # 1, with explanations in blue. Solve: (14.76 – 14)/0.280

PEMDAS

Numerator: Subtraction rule , then division rule

(14.76 – 14) = 0.76

0.76 ( 1 sig fig) /0.28 = 2.714

Correct answer = 2.714 rounded to 3

Solve 27.3 + 16.00/5 = 27.3 + 3.2 = 30.5

Order of operations: division first, followed by addition

16.00/5 = 3.2

27.3 + 16.00/5 = 27.3 + 3.2 = 30.5

Correct answer = 30.5 rounded to 31 or 3.1 x 101.

Example 3: A bit more complicated.

2000 – 14/3.2

Order of operations: Division, followed by subtraction

14/3.2 = 4.375 ( )

2000 – 4.375 = 1995.625 = 2000 ( rounded to 1 sig fig)

(2000 has 1 sig fig, no decimals, least accurate number, so the answer has to be reported to same # of figs as the least accurate number)

Question 22

What is 38.763/5.1 + 509.15 to the correct number of significant figures? Help: Complex Calculation Examples chem125-1b - Fluff Butt Reviews

Explanation

PEMDAS (this is your main bae never forget) 38.763/5.1 = 7.6006 ( 2 sig figs according to the division rule) 7.6006 + 509.15 = 516.75 (remember to go the least accurate (+ rule)) Final Answer with rounding = 516.8

Question 23

What is (53+8601.8)/54 to the correct number of significant figures? chem125-1b - Fluff Butt Reviews

Explanation

PEMDAS bbs (53 + 8601.8) = 8654.8 ( least accurate is 53 with no decimal place) 8654.8/54 = 160.27 (54 has only 2 sig figs) Dun dun dun the final answer is 160 ( who would known it’s not like it isn’t to the left or anything)