Honors Chem. U1 Atoms & Elements

All matter can be broken down into pure substances or mixtures.

• True
• False

Pure substances include (select all that apply)...

• elements
• molecules
• solutes
• solvents

Any sample of an element will always have the same _____ _____, no matter the sample size.

• average ratio
• number of protons
• number of electrons
• average mass

Any sample of a molecule will always have the same _____ _____, no matter the sample size.

• average ratio
• number of protons
• number of electrons
• average mass

In chemical analysis, scientists use a mass spectrometer to find the ________ ______ of each element in the compound.

• mass ratio
• percent mass
• ionization energy
• electron affinity

The percent mass is used to find the composition, empirical formula, and purity of a substance.

• True
• False

Using a periodic table, how can you find the amount of grams of an element that are in 1 mol of that element?

• Look for the average atomic weight (g).
• Look for the atomic number
• Divide the group number by the period number.
• Look for the average atomic mass (g).

You can use a unit conversion factor to convert the percent mass to moles.

• True
• False

What is Avogadro's number?

In a chemical formula, how is the number of moles represented?

• using subscripts for each element
• you can't represent the number of moles in a chemical formula
• using coefficients in front of each molecule
• multiply the coefficient by Avogadro's number