Chemistry Constants (Quick Reference)

Notes

• Exact by SI definition: Avogadro’s number, elementary charge, speed of light, Planck’s constant, and Boltzmann constant.
• The atomic mass unit value follows CODATA recommended values and is shown to common student-use precision.
• Gas-law constants are grouped by units so students can choose the version that matches pressure and volume units.
• Acid-base values such as K_w and pK_w are for 25 °C unless otherwise noted.
• Use the search box to quickly find constants by name, symbol, units, or context such as “gas law,” “electrochemistry,” or “pH.”