Fundamentals of Chemistry

What is matter and how is it classified?

• Matter is classified into pure substances (elements and compounds) and mixtures (homogeneous and heterogeneous).

• Matter is only classified as solids and liquids.

• Matter is defined as anything that can be seen or touched.

• Matter consists solely of gases and plasma.

State the law of conservation of mass.

• Mass can be created in a closed system.

• Mass is destroyed during chemical reactions.

• Mass is conserved in a closed system; it is neither created nor destroyed.

• Mass varies depending on the temperature.

What is the mole concept and its significance in chemistry?

• The mole concept is only used for gases in chemistry.

• The mole concept is a method for quantifying substances in chemistry, significant for relating mass to the number of particles.

• The mole concept measures temperature in chemical reactions.

• The mole concept is irrelevant to stoichiometry.

How do you calculate the atomic mass of an element?

• Atomic mass is determined by the element's position on the periodic table.

• Atomic mass is calculated by averaging the number of electrons in an element.

• Atomic mass is calculated by summing the weighted average of the masses of an element's isotopes.

• Atomic mass is the total number of protons in an atom.

Define molecular mass and how it differs from atomic mass.

• Molecular mass refers to the mass of an ion, while atomic mass is the mass of a molecule.

• Molecular mass is the mass of a single atom, while atomic mass is the total mass of a molecule.

• Molecular mass is the average mass of all isotopes of an element, while atomic mass is the mass of a molecule.

• Molecular mass is the total mass of a molecule, while atomic mass is the mass of a single atom.

What is an empirical formula? Provide an example.

• The empirical formula of water (H2O) is H2O2.

• For example, the empirical formula of glucose (C6H12O6) is CH2O.

• The empirical formula of sodium chloride (NaCl) is Na2Cl2.

• The empirical formula of ethanol (C2H5OH) is C2H5O.

How do you determine the molecular formula from the empirical formula?

• Molecular formula = Empirical formula + Molar mass of compound

• Molecular formula = (Empirical formula subscripts) - (Molar mass of compound / Molar mass of empirical formula)

• Molecular formula = Empirical formula x Molar mass of empirical formula

• Molecular formula = (Empirical formula subscripts) x (Molar mass of compound / Molar mass of empirical formula)

Explain the law of definite proportions with an example.

• The law of definite proportions states that all compounds have the same mass.

• The law of definite proportions is illustrated by carbon dioxide (CO2) containing equal parts of carbon and oxygen.

• The law of definite proportions applies only to gases and not to liquids or solids.

• The law of definite proportions is exemplified by water (H2O), which always contains 2 grams of hydrogen for every 16 grams of oxygen.

What is the relationship between moles and mass in a substance?

• Moles are directly proportional to mass, calculated using the formula: mass = moles × molar mass.

• Moles and mass are unrelated quantities.

• Mass is calculated by dividing moles by molar mass.

• Moles are inversely proportional to mass.

How do you convert between moles and molecules?

• Multiply molecules by 6.022 x 10^23 to get moles

• Subtract 6.022 x 10^23 from molecules to get moles

• Multiply moles by 6.022 x 10^23 to get molecules; divide molecules by 6.022 x 10^23 to get moles.

• Add 6.022 x 10^23 to moles to get molecules