03/14 Chemical Composition and the Mole Free Online FlashCards

What information does a chemical formula communicate?

A chemical formula uses element symbols and subscripts to show which elements are present and their relative or exact numbers of atoms, ions, or formula units.

How do subscripts and coefficients differ?

A subscript applies to the preceding element or group, while a coefficient multiplies the entire formula. Thus, 3H₂O contains six H atoms and three O atoms.

How many atoms of each element are in Ca(NO₃)₂?

Ca(NO₃)₂ contains 1 Ca atom, 2 N atoms, and 6 O atoms. The subscript 2 outside the parentheses multiplies every atom in the nitrate group.

What is the neutral formula for aluminum oxide?

Al₂O₃. Two Al³⁺ ions provide +6 charge and three O²⁻ ions provide −6 charge, giving an electrically neutral compound.

Name FeCl₃.

Iron(III) chloride. Three Cl⁻ ions require Fe³⁺, so the Roman numeral III identifies iron’s charge.

Name CO₂.

Carbon dioxide. The prefix di- indicates two oxygen atoms; mono- is usually omitted for the first element.

What naming patterns distinguish binary acids and oxyacids?

Binary acids use hydro- + the element root + -ic acid. Oxyacids from -ate anions end in -ic acid, while those from -ite anions end in -ous acid.

How many specified entities are in one mole?

One mole contains exactly 6.02214076 × 10²³ specified entities. The entities may be atoms, molecules, ions, or formula units.

How many H₂O molecules are in 0.250 mol H₂O?

0.250 mol H₂O × 6.022 × 10²³ molecules/mol = 1.51 × 10²³ H₂O molecules.

What is the molar mass of H₂O?

M(H₂O) = 2(1.008) + 16.00 = 18.016 g/mol, commonly rounded to 18.02 g/mol.

What equation converts mass to moles?

n = m/M, where n is amount in moles, m is mass in grams, and M is molar mass in grams per mole.

What is the percent by mass of hydrogen in water?

%H = (2.016 g H ÷ 18.02 g H₂O) × 100% = 11.19%.