formulae, equations and amount of substance

• What is Avogadro's number?

  1. 6.02 x 10$^{23}$ particles
• What does one mole of a substance contain?

  1. 02 x 10$^{23}$ atoms or molecules
• How do you calculate the number of particles in a substance?

  Avogadro's number times the number of moles
• How many particles are in 0.67 moles of ammonia (NH₃)?

  1. 03 x 10$^{23}$ particles
• What is the formula to calculate the number of moles from mass and Mr?

  Number of moles = mass / molecular mass
• Calculate the number of moles in 23 g of gold (AR = 197).


  0.12 moles
• What is the significance of significant figures in calculations?

  Precision in reporting numerical results
• How can you rearrange the moles formula?

  To find mass or molecular mass
• How do you calculate the number of moles in a solution?

  Concentration times volume
• What is the volume unit required for calculating moles in a solution?

  Decimeters cubed
• Calculate the number of moles in 200 cm³ of 0.35 moles/dm³ HCl.

  0.07 moles
• What is the empirical formula?

  Simple whole number ratio of elements
• How do you find the empirical formula from percentages of elements?

  Convert percentages to masses, then to moles
• What is the empirical formula for a compound with 23.3% magnesium, 30.7% sulfur, and 46.0% oxygen?

  MgSO₃
• How do you convert an empirical formula to a molecular formula?

  Divide molecular mass by empirical mass
• How do you determine the empirical formula from combustion products?

  Use masses of combustion products to find moles
• What do ionic equations show?

  Which ions are formed in solution
• What is the simplified ionic equation for the reaction of sulfuric acid and potassium hydroxide?

  H⁺ + OH^- → H₂O
• What are spectator ions?

  They do not participate in the reaction
• How do you calculate theoretical mass from a balanced equation?

  Use the molar ratios from the equation
• How much calcium oxide can be made from 34 g of calcium?

  Calculate using the balanced equation
• What is an aquis in chemistry?

  Anything dissolved in water
• Why are balanced equations used in theoretical mass calculations?

  To determine the mass of products formed
• How much calcium oxide can be produced from 34 g of calcium?

  47.6 g of calcium oxide
• What is the molar mass of calcium?

  40 g/mol
• What is the molar mass of calcium oxide?

  56 g/mol
• How do you calculate the theoretical mass of calcium oxide from calcium?

  Divide calcium mass by 80, then multiply
• What is a theoretical mass?

  The maximum amount of product possible
• What are displacement reactions?

  • More reactive element displaces less reactive
  • Example: F2 + NaBr → NaF + Br2
• What happens in acid-base reactions?

  • An acid reacts with a base
  • Produces salt and water
  • Example: HNO3 + KOH → KNO3 + H2O
• What do spectator ions do in ionic equations?

  They do not change during the reaction
• What is produced when carbonates react?

  Carbon dioxide
• What is a precipitation reaction?

  • Solid produced from two aqueous reactants
  • Example: BaCl2 + K2SO4 → BaSO4 (solid) + KCl (aqueous)
• What is the molar gas volume at standard room temperature and pressure?

  24 dm³/mol
• How do you calculate the number of moles of gas?

  Volume in dm³ divided by molar gas volume
• What is the number of moles in 7.8 dm³ of gas at standard room temperature?

  0.325 moles
• What is the ideal gas equation?

  • PV = nRT
  • P = pressure (Pa)
  • V = volume (m³)
  • n = number of moles
  • R = gas constant (8.31 J/(K·mol))
  • T = temperature (K)
• How do you convert volume from m³ to cm³?

  Multiply by 1,000,000
• What is the standard temperature for gas calculations?

  273 Kelvin
• What is the relationship between moles and mass for gases?

  Moles = mass / molar mass