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Questions and Answers
Which of the following would be classified as a mixture?
All of the following are heterogeneous mixtures except:
The correct classifications for air, seawater, helium, and concrete respectively are:
Which of the following observations are due to physical changes?
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Filtration is the process used to:
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Which of the following statements is incorrect?
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What are the number of electrons, protons, and neutrons in a neutral atom of the isotope uranium with mass number 235 and atomic number 92?
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What do 10Ne, 9F, and 20Na have in common regarding their neutral atom properties?
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Which of the following statements is true for neutral atoms?
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What are the percentage abundances of the isotopes Ga-69 and Ga-71 if the molar mass of gallium is 69.72 g mol–1?
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What is the atomic mass of the other isotope of rubidium if one has an atomic mass of 86.92 a.m.u. and the observed chemical atomic mass is 85.47?
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Which of the following is an empirical formula?
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Which of the following is NOT an example of a chemical reaction?
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Express the temperature 422.35 K in degrees Celsius.
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Which of the following has 18 neutrons and 18 electrons?
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Which of the following species has 48 electrons?
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Study Notes
Heterogeneous Mixtures
- A heterogeneous mixture is a mixture where the components are not evenly distributed throughout the mixture.
- Examples of heterogeneous mixtures include:
- mud
- a rock
- sour cream
- a precipitate in water
Mixtures
- Mixtures are substances that are made up of two or more components that are not chemically bonded together.
- Examples of mixtures include:
- seawater
- air
- concrete
Elements and Compounds
- An element is a pure substance that cannot be broken down into simpler substances by chemical means.
- A compound is a pure substance that is made up of two or more elements that are chemically bonded together.
- Examples of elements:
- Iron (Fe)
- Nitrogen (N)
- Examples of compounds:
- Water (H2O)
- Sodium chloride (NaCl)
Physical and Chemical Changes
- A physical change is a change in the form or appearance of a substance, but not its chemical composition.
- A chemical change is a change that results in the formation of a new substance with a different chemical composition.
- Examples of a physical change:
- water changing from a liquid to a solid (ice)
- Examples of chemical changes:
- burning a match
Filtration
- Filtration is a process used to separate a solid from a liquid
Molecules
- A molecule is formed when two or more atoms bond together.
- Examples of molecules include:
- Nitrogen (N2)
- Water (H2O)
Representing Elements, Compounds, and Mixtures
- An element can be represented by a single atom (X).
- A compound can be represented by a group of atoms that are bonded together (Y).
- A mixture can be represented by a combination of different elements and compounds (Z).
Isotopes and Atomic Structure
- Isotopes are atoms of the same element with the same number of protons (atomic number) but different numbers of neutrons.
- Atomic number of an element is the number of protons in the nucleus of an atom.
- Mass number of an atom is the sum of protons and neutrons in the nucleus.
- Neutral atoms have the same number of electrons and protons.
Molar Mass and Isotopic Abundance
- Molar mass is the mass of one mole of a substance.
- Isotopic abundance is the percentage of each isotope found in a naturally occurring sample of an element.
- The molar mass of an element is the average of the masses of its isotopes, weighted by their abundances.
- Formula for calculating molar mass: (Isotope AM 1 x % Abundance) + (Isotope AM 2 x % Abundance) /100
Empirical Formula
- Empirical formula represents the simplest whole-number ratio of atoms in a compound.
Chemical Reactions
- Chemical reactions involve the formation or breaking of chemical bonds.
- Dissolution, condensation, burning, rusting, and mixing of chemical solutions can all be examples of chemical reactions.
Temperature Scales
- Kelvin (K) and Celsius (°C) are common temperature scales.
- Conversion Formula: K = °C + 273.15
Number of Electrons, Protons, and Neutrons
- The number of neutrons in an atom can be calculated by subtracting the atomic number from the mass number.
- The number of electrons in a neutral atom is equal to the number of protons.
Determining Number of Electrons in Ions
- Ions are atoms that have gained or lost electrons.
- Cations are positively charged ions formed by losing electrons.
- Anions are negatively charged ions formed by gaining electrons.
- To determine the number of electrons in an ion, add or subtract the number of electrons gained or lost from the neutral atom.
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Description
Test your knowledge on heterogeneous mixtures, mixtures, elements, and compounds. This quiz also covers the distinctions between physical and chemical changes. Perfect for students looking to reinforce their understanding of these fundamental chemistry concepts.
