1,001 Chemistry Practice Problems For Dummies (2014)
Part I. The Questions
Chapter 2. Scientific Notation and Significant Figures
Scientific notation allows you to write very large and very small numbers, which are common in chemistry, in a simplified manner. Many chemical experiments involve very precise measurements. The significant figures are an indication of the precision of these measurements. In calculations involving more than one measurement, you need to maintain the precision inherent in the significant figures.
The Problems You’ll Work On
In this chapter, you work with scientific notation and significant figures in the following ways:
Expressing numbers in standard and scientific notation
Doing calculations with numbers in scientific notation
Determining significant figures
Combining math operations with significant figures
What to Watch Out For
Remember the following when working on scientific notation and significant figures:
All nonzero digits and zeroes between nonzero digits are significant. Zeroes to the left in the number (leading zeroes) are never significant. Zeroes to the right are significant only if they aren’t just indicating the power of ten.
Don’t confuse the addition/subtraction rule with the multiplication/division rule. Be extra careful when solving mixed-operation problems.
Most calculators convert to and from scientific notation, but double-check the answer. Calculators are complete idiots concerning the rules for significant figures.
Putting Numbers in Scientific Notation
76–80 Express the given number in scientific notation.
76. 876
77. 4,000,001
78. 0.000510
79. 900 × 104
80. 10
Taking Numbers out of Scientific Notation
81–85 Convert the given number to nonscientific notation (regular decimal form).
81. 2.00 × 102
82. 9 × 10–2
83. 4.7952 × 103
84. 1.64 × 10–5
85. 0.83 × 10–1
Calculating with Numbers in Scientific Notation
86–105 Complete the calculations and record your answer in scientific notation. (If you use a calculator, choose a mode that doesn’t put the numbers in scientific notation for you.)
86. (1.26 × 103) + (4.71 × 103) =
87. (3.9 × 10–1) + (2.1 × 10–1) =
88. (8.9 × 102) – (3.3 × 101) =
89. (7.4 × 10–1) – (5.2 × 101) =
90. (8.240 × 102) + (3.791 × 102) =
91. (1.00 × 107) – (5.2 × 105) =
92. (5.42 × 10–3) + (6.19 × 10–4) =
93. (8.20 × 106) – (7.31 × 104) + (2.846 × 105) =
94. (1.0 × 10–7) × (4.5 × 105) =
95. (1.0 × 10–3) ÷ (1.0 × 10–4) =
96. (3.15 × 1012) × (2.0 × 103) =
97. (4.7 × 10–2) ÷ (9.6 × 10–7) =
98. (8.40 × 1015) × (2.00 × 10–5) =
99. (1.0 × 108) ÷ (3.2 × 102) =
100. (9.76 × 10–9) × (3.55 × 10–3) ÷ (1.8 × 10–5) =
101. (2.48 × 103) × (4.756 × 10–4) × (9.1 × 10–2) =
102. (1.8 × 10–4) + (6.27 × 10–2) × (2.9 × 10–3) =
103. (9.189 × 10–19) ÷ (0.6021 × 10–13) + (4.5 × 10–11) =
104. (4.115 × 102) + (1.1 × 101) ÷ (3.68 × 10–6) ÷ (8.2 × 104) =
105. 
Recognizing Significant Figures
106–115 Indicate how many significant figures (significant digits) are in the given number.
106. 343
107. 0.4592
108. 705,204
109. 0.0075
110. 248,000
111. 9,400,300
112. 1.0070
113. 3,000,000.0
114. 0.0040800
115. 0.870
Writing Answers with the Right Number of Sig Figs
116–135 Complete the calculation and express your answer using the correct number of significant figures.
116. 5,379 + 100 =
117. 12.4 + 0.59 =
118. 61.035 – 33.48 =
119. 71 + 24.87 + 0.0003 =
120. 0.387 – 467 =
121. 0.005689 + 0.0410 =
122. 60.0080 – 128.35429 + 7.941 =
123. 130 + 4,600 + 395.2 =
124. 0.0074 ÷ 0.000035 =
125. 75 × 349 =
126. 7.98 × 5.21 =
127. 5.00 ÷ 0.0025 =
128. 7.0 cm × 7 cm =
129. 6.48 ÷ 194.21 =
130. 0.000000029 × 0.00000745 =
131. 
132. 2,300.00 × 0.854 + 110 =
133. 
134. 
135. 