Matter and its properties
What is the difference between a physical and chemical property?
A physical property can be observed without changing the substance’s identity, while a chemical property can only be observed by changing the substance’s chemical identity.
What is an isotope?
Isotopes are atoms of the same element with different numbers of neutrons, thus differing in atomic mass.
What is a covalent bond?
A covalent bond is a chemical bond that involves the sharing of electron pairs between atoms.
What is the correct name for the compound CO2?
carbon dioxide
What is the molar mass of water H2O?
18.02 g/mol.
What is the difference between intrinsic and extrinsic properties? (give an example for each)
Intrinsic: do not depend on the amount of matter in a sample. They are inherent to the substance itself.
- Density, boiling point and melting point, color, hardness, conductivity
Extrinsic: depend on the amount of matter in a sample. They change when the size of the sample changes.
- mass, volume, length, total charge
What is an ion?
An ion is an atom or molecule with a net electric charge due to the loss or gain of one or more electrons.
Which element is more electronegative: fluorine or oxygen?
Fluorine.
What is the formula for sodium chloride?
NaCl
Define molarity and write the equation used when diluting solutions
Molarity is the number of moles of solute per liter of solution. M1V1 = M2V2
How can you distinguish between a homogeneous mixture and a compound based on their properties?
A homogeneous mixture consists of two or more substances physically combined and can be separated by physical means (e.g., filtration, distillation), while a compound is made up of elements chemically bonded and can only be separated into its components through chemical reactions. Homogeneous mixtures retain the properties of their components, whereas compounds have entirely new properties distinct from the elements that form them.
Calculate the average atomic mass of chlorine if 75% of its atoms are chlorine-35 and 25% are chlorine-37.
Average atomic mass = (0.75 × 35) + (0.25 × 37) = 35.5 amu.
Define ionization energy and its trend on the periodic table.
Ionization energy is the energy required to remove an electron from an atom in the gas phase. Increases down a period and up a family.
Name the compound PCl3.
Phosphorus trichloride
How many moles of oxygen are required to react with 4 moles of hydrogen to form water?
2 moles of oxygen.
Classify each as an element, compound, homogeneous mixture, or heterogeneous mixture: Saltwater, carbon dioxide, iron, pizza.
Saltwater - homogeneous mixture, Carbon dioxide - compound, Iron - element, Pizza - heterogeneous mixture.
How many protons, neutrons, and electrons are in the ion O2- if its atomic number is 8?
Protons = 8, Neutrons = 8, Electrons = 10.
Explain the octet rule.
The octet rule states that atoms tend to bond in a way that gives them a full valence shell, typically consisting of 8 electrons.
Write the formula for calcium nitrate.
Ca(NO3)2
In a reaction, if 5.00 g of CaCl2 is dissolved in water, what is the molarity of the solution in 100 mL of water? (Molar mass of CaCl2 = 110.98 g/mol).
Molarity = 0.450 M.
What are intensive and extensive properties? Give an example of each.
Intensive properties do not depend on the amount of substance (e.g., density), while extensive properties depend on the amount of substance (e.g., mass).
What does the term “mass number” refer to in isotopes?
Mass number refers to the total number of protons and neutrons in the nucleus of an atom.
What is the difference between a polar covalent bond and a nonpolar covalent bond?
A polar covalent bond occurs when electrons are shared unequally between atoms due to a difference in electronegativity, causing a partial positive and partial negative charge on opposite ends of the bond. A nonpolar covalent bond occurs when electrons are shared equally because the atoms have similar or equal electronegativities, resulting in no charge separation across the bond.
What is the name of the compound H2SO4?
sulfuric acid
A reaction has a theoretical yield of 10.0 g but the actual yield is 7.5 g. What is the percent yield?
Percent yield = (7.5/10.0)×100=75%.