Accelerated Chemistry Practice Studio

Unit 2: Measurement, Chemical Formulas, Molar Quantities, & Dimensional Analysis.

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Chemistry Reference Center

Transition (3d)

Select any element cell above to inspect its atomic properties, molar mass, and common charges.

Physical Constants & Molar Conversions

Avogadro's Number (N_A)6.022 × 10²³ particles/mol

Molar Volume of Ideal Gas at STP22.414 L/mol (0 °C, 1 atm)

Atomic Mass Unit (amu)1 amu = 1.6605 × 10⁻²⁴ g

Microgram Conversion1 g = 1.0 × 10⁶ μg (10⁻⁶ g/μg)

Milligram Conversion1 g = 1.0 × 10³ mg

Kilogram Conversion1 kg = 1.0 × 10³ g

Common Polyatomic Ions & Charges

Ammonium (NH₄⁺)+1 charge

Hydroxide (OH⁻)-1 charge

Nitrate (NO₃⁻)-1 charge

Nitrite (NO₂⁻)-1 charge

Hydrogen carbonate / Bicarbonate (HCO₃⁻)-1 charge

Acetate (C₂H₃O₂⁻)-1 charge

Carbonate (CO₃²⁻)-2 charge

Sulfate (SO₄²⁻)-2 charge

Sulfite (SO₃²⁻)-2 charge

Phosphate (PO₄³⁻)-3 charge

Binary Covalent Numerical Prefixes

1: mono- (never on first element)6: hexa-

2: di-7: hepta-

3: tri-8: octa-

4: tetra-9: nona-

5: penta-10: deca-

Key Quantitative Formulas

Percent Composition (% by mass)(mass of element / total molar mass) × 100%

Moles from Massn = mass (g) / molar mass (g/mol)

Particles from Molesparticles = n × 6.022 × 10²³

Gas Volume at STPV = n × 22.414 L

Molecular Multiple (n)Molar Mass / Empirical Formula Mass

Significant Figures Rules

Multiplication / DivisionRound to fewest total significant figures.

Addition / SubtractionRound to fewest decimal places (least precise place).

Leading Zeros (e.g. 0.0042)Never significant (placeholders only).

Captive Zeros (e.g. 50.04)Always significant.

Trailing Zeros (e.g. 45.00 vs 4500)Significant only if a decimal point is written.

⠿ Scientific Mini-Calc

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