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Questions and Answers
What is the molecular formula for water?
What is the molecular formula for water?
The melting point of H2O is 0.0 °C.
The melting point of H2O is 0.0 °C.
True
The boiling point of H2O is 90.0 °C.
The boiling point of H2O is 90.0 °C.
False
What type of change is indicated if Substance X changes from one sketch to another?
What type of change is indicated if Substance X changes from one sketch to another?
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What do you need to determine from the sketches of substances?
What do you need to determine from the sketches of substances?
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Count the significant digits in 0.003000 J.
Count the significant digits in 0.003000 J.
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What is the rounded mass of the sample shown on the scale 0023.43 g to 3 significant digits?
What is the rounded mass of the sample shown on the scale 0023.43 g to 3 significant digits?
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Write 7.977 x 10^-2 as a decimal.
Write 7.977 x 10^-2 as a decimal.
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What is the product of (2.3 x 10^-3)(-3.0 x 10^-2)?
What is the product of (2.3 x 10^-3)(-3.0 x 10^-2)?
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How many hydrogen atoms are in each formula unit of ammonium carbonate, (NH4)2CO3?
How many hydrogen atoms are in each formula unit of ammonium carbonate, (NH4)2CO3?
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Write the chemical formula for sulfur dichloride.
Write the chemical formula for sulfur dichloride.
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Write the chemical formula for acetic acid.
Write the chemical formula for acetic acid.
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What is the net electric charge of this object?
What is the net electric charge of this object?
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Write the symbols for the elements with an atomic number greater than 55 and atomic mass less than 140.6 u.
Write the symbols for the elements with an atomic number greater than 55 and atomic mass less than 140.6 u.
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How many protons and electrons are in a neutral atom of calcium?
How many protons and electrons are in a neutral atom of calcium?
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What is the group number of sodium, and in which period does it belong?
What is the group number of sodium, and in which period does it belong?
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What is a period on the periodic table?
What is a period on the periodic table?
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What is a group on the periodic table?
What is a group on the periodic table?
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What is the electron configuration for a neutral atom of magnesium?
What is the electron configuration for a neutral atom of magnesium?
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How many valence electrons are in a neutral atom of aluminum?
How many valence electrons are in a neutral atom of aluminum?
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How do you find valence electrons?
How do you find valence electrons?
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How many valence electrons are in a neutral atom of xenon (Xe)?
How many valence electrons are in a neutral atom of xenon (Xe)?
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What is the chemical symbol for an element in Period 3 Group 3A?
What is the chemical symbol for an element in Period 3 Group 3A?
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How many protons are in a neutral atom of lanthanum (La)?
How many protons are in a neutral atom of lanthanum (La)?
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Study Notes
Molecular Compounds and State Changes
- Pure molecular compound: Water (H₂O)
- Melting point: 0.0 °C; Boiling point: 100.0 °C
- Visualization of molecular structures shows changes at different temperatures.
Physical vs. Chemical Changes
- Identification of changes to a substance (Substance X) under a microscope.
- Distinctions between possible physical changes and chemical changes must be made.
Pure Substances Classification
- Classification of sketches of substances as elements, compounds, or mixtures based on microscopic views.
Significant Digits
- Important to count significant digits in measurements for accuracy.
- Examples:
- 0.003000 J (4 significant digits)
- 2.1 x 10^-3 mL (2 significant digits)
- -9.0 x 10^-2 kJ/mol (3 significant digits)
-
- kg (5 significant digits)
Rounding and Scientific Notation
- Rounding measurements to 3 significant digits (e.g., 0023.43 g to 23.4 g).
- Conversion of scientific notation:
- 7.977 x 10^-2 = 0.07977
- 0.004209 = 4.209 x 10^-3
Calculations in Scientific Notation
- Multiplication example: (2.3 x 10^-3) * (-3.0 x 10^-2) = -6.9 x 10^-5.
Density, Mass, and Volume
- Use of sketches to deduce mass, volume, and density for objects in specific scenarios.
Composition of Substances
- Classification of pure substances as either elements or compounds based on atomic structure.
Chemical Formulas
- Ammonium carbonate (NH₄)₂CO₃ contains 8 hydrogen atoms.
- Given molecules:
- SOCl₂ (sulfur dichloride)
- C₂H₄O₂ (acetic acid)
Electric Charge and Atomic Structure
- The net electric charge of a neutral object is 0.
- Calcium (Ca) has 20 protons and 20 electrons.
Periodic Table Information
- Sodium (Na) is located in Period 3, Group 1A.
- Periods = horizontal rows, Groups = vertical columns.
- Aluminum (Al) belongs to Period 3, Group 3A.
- Elements in Period 2, Group 2A include Beryllium (Be).
- Lanthanum (La) has 57 protons and electrons.
Element Families
- Bromine and Lithium belong to specific element families (e.g., Halogens and Alkali Metals).
Electron Configuration
- Electron configuration for magnesium and phosphorus to illustrate electron distribution.
Valence Electrons
- Aluminum has 3 valence electrons; Xenon (Xe) has 8 valence electrons.
- Valence elections can be deduced from the group the element occupies.
Chemical Symbols and Formulas
- Symbols for elements in various periods/groups must be written correctly.
- Complete chemical formulas should include physical state symbols (s, l, g, aq).
Ionic and Molecular Compounds
- Classification of compounds as ionic or molecular based on their properties.
- Empirical formulas should be provided for binary ionic compounds formed from given ions.
Cationic and Anionic Symbols
- Knowledge of ionic species symbols is essential for writing compound formulas.
Compound Formation
- Determine whether pairs of elements form ionic compounds; if so, provide empirical formulas and names.
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