Atomic Structure and Periodic Table
What is the difference between atomic number and mass number?
The atomic number (Z) represents the number of protons in an atom, while the mass number (A) is the sum of protons and neutrons in the nucleus.
How do you determine the molecular formula from an empirical formula?
The molecular formula is a whole-number multiple of the empirical formula, determined using the molar mass.
What is Avogadro’s number, and why is it important in chemistry?
Avogadro’s number (6.022 × 10²³) represents the number of particles (atoms, molecules, or ions) in one mole of a substance.
What are the steps to balance a chemical equation?
Identify reactants and products, count atoms of each element, adjust coefficients, and verify that the equation is balanced.
What is the purpose of using significant figures in scientific measurements?
Significant figures reflect the precision of a measurement and help ensure accuracy in calculations.
The subatomic particles found in the nucleus of an atom are called ______ and ______.
Protons, neutrons.
Ionic compounds are formed between two nonmetals.
False (they are formed between a metal and a nonmetal).
The molar mass of CO₂ is ______ g/mol.
44.01 g/mol.
Changing the subscripts in a chemical formula is an acceptable way to balance an equation.
False
In scientific notation, 0.00034 can be written as 3.4 × 10-5.
False, it would be In scientific notation, 0.00034 can be written as 3.4 × 10-4.
Isotopes of an element have the same number of protons but different numbers of neutrons.
True.
The correct name for the compound SF6 is ______.
Sulfur hexafluoride.
One mole of H₂O contains twice as many hydrogen atoms as oxygen atoms.
True.
In a combustion reaction, a hydrocarbon reacts with ______ to produce CO₂ and H₂O.
Oxygen (O₂)
The SI unit for mass is ______, and the SI unit for volume is ______.
Kilogram (kg), cubic meters (m3).
Why are noble gases mostly non-reactive?
Noble gases have a full valence electron shell, making them stable and unlikely to react with other elements.
What is the difference between a molecular compound and an ionic compound?
Molecular compounds are made of nonmetals and share electrons (covalent bonds), whereas ionic compounds involve the transfer of electrons between metals and nonmetals.
How do you determine the percent composition of an element in a compound?
Divide the total mass of the element in the compound by the molar mass of the entire compound and multiply by 100%.
What is the difference between a reactant and a product in a chemical equation?
Reactants are substances that start a reaction, while products are the substances formed after the reaction.
How do you convert 450 mg to kg?
Convert mg to g (450 mg = 0.450 g), then g to kg (0.450 g = 0.00045 kg).
The elements on the right side of the periodic table are called ______, while those on the left are called ______.
Nonmetals, metals.
The correct formula for selenium hexafluoride is ______.
SeF6
The empirical formula of a compound that is 40% carbon, 6.7% hydrogen, and 53.3% oxygen by mass is ______.
CH₂O
The balanced equation for the reaction of propane (C₃H₈) with oxygen is ______.
C₃H₈ + 5O₂ → 3CO₂ + 4H₂O.
The density of a substance is calculated using the formula ______.
Density = Mass/Volume.