Untitled Flashcard Set

Avogadro’s number

6.022 × 10²³ mol⁻¹, representing the number of particles in one mole of a substance.

Moles of water in 2.00 moles

2.00 moles of water contains 1.20 × 10²⁴ molecules.

Molar mass of carbon dioxide (CO₂)

The mass of one mole of CO₂ is 44.0 g.

Grams to moles conversion for water

18.0 grams of water (H₂O) equals 1.00 mole.

Atoms in 0.25 moles of sodium (Na)

There are 1.51 × 10²³ atoms in 0.25 moles of sodium.

Moles of ammonia from molecules

A sample with 1.51 × 10²⁴ molecules of ammonia contains 2.51 moles.

Mass of 0.50 moles of NaCl

0.50 moles of sodium chloride (NaCl) has a mass of 29.25 g.

Formula units in calcium carbonate (CaCO₃)

5.00 grams of CaCO₃ contains approximately 3.01 × 10²² formula units.

Importance of the mole concept

The mole concept allows chemists to count atoms/molecules by weighing them.

Mass of one mole of glucose (C₆H₁₂O₆)

One mole of glucose has a mass of approximately 180 grams.

Information from mass spectrum

A mass spectrum provides identities and relative abundances of isotopes present in a sample.

Distinguishing isotopes in mass spectrometry

Mass spectrometers distinguish isotopes based on different mass-to-charge ratios.

Major peaks in mass spectrum

Indicates that the element has at least two naturally occurring isotopes.

Average atomic mass and whole numbers

Average atomic mass is not whole due to the weighted average of isotopes.

Calculating average atomic mass

Average atomic mass is calculated by summing the products of mass and percent abundance for each isotope.

Weighted average of isotopic masses

The weighted average of isotopic masses relates to the periodic table value for atomic mass.

Why singly charged ions in mass spectra

Singly charged monatomic ions simplify analysis without complications from multiple charges.

Estimating percent abundance with mass spectrum

Percent abundance is estimated by comparing peak heights in the mass spectrum.

Empirical formula definition

The empirical formula shows the simplest whole number ratio of atoms in a compound.

Law of definite proportions

A chemical compound always contains its constituent elements in a fixed mass ratio.

Molecular vs empirical formula

Molecular formula shows actual atom counts, while empirical formula shows simplest ratios.

Determining empirical formula from composition

Calculate moles of each element, divide by smallest to find simplest ratios.

Smallest whole number ratios in empirical formulas

Empirical formulas are reduced to the smallest whole number ratios for clarity.

Percent by mass calculation

Percent by mass is determined by dividing the mass of an element by the total mass, then multiplying by 100%.

Formula unit of NaCl significance

NaCl indicates a 1:1 ratio of sodium to chlorine atoms.

Empirical formula from mass composition

Given percentages, convert to moles, divide by smallest to find mole ratios.

Ionic compounds and molecular formulas

Ionic compounds use formula units as they exist as lattices of ions, not discrete molecules.

Ratio of potassium to oxygen in K₂O

The formula K₂O indicates a 2:1 ratio of potassium to oxygen.

Importance of knowing component mass in mixtures

Knowing masses ensures accurate stoichiometry in reactions and predicts products.

Difference between pure substances and mixtures

Pure substances have fixed compositions, while mixtures can vary in component ratios.

How elemental analysis identifies purity

Elemental analysis shows fixed ratios for pure substances and varying ratios for mixtures.

Percent by mass of sodium chloride in a mixture

The percent by mass of sodium chloride in a mixture containing 15.0 g NaCl and 10.0 g KCl is 60%.

Reactivity and periodic trends

Reactivity is influenced by valence electrons and predicts chemical behavior of elements.

Definition of ionization energy

Ionization energy is the energy required to remove the outermost electron from a gaseous atom.

Effect of distance on ionization energy

Ionization energy decreases with increased distance between electron and nucleus.

Comparison of ionization energy in Li and Na

Li has a higher ionization energy than Na due to its outer electron being closer to the nucleus.

Trends in ionization energy across periods

Ionization energy increases across a period due to increasing nuclear charge.

Trends in ionization energy down groups

Ionization energy decreases down a group as atoms are larger and more shielded.

What is effective nuclear charge?

Effective nuclear charge is the net positive charge felt by valence electrons, accounting for shielding.

Concept of electronegativity

Electronegativity is the ability of an atom to attract electrons in a chemical bond.

Understanding of periodicity

Periodicity refers to the repeating patterns in element properties on the periodic table.

Relationship between electron configuration and periodic table position

Electron configuration determines an element's group and period in the periodic table.