AP Cem ch1

• What are significant figures in a number?

  All non-zero digits are significant figures.
• When are zeros considered significant figures?

  Zeros in the middle of a number are always significant.
• Under what condition are zeros after non-zero digits considered significant?

  Zeros after non-zero digits are significant only if there is a decimal point present.
• How do you round numbers in multiplication and division?

  You round to the lowest number of significant figures
• How do you round numbers in addition and subtraction?

  You round to the lowest decimal places
• What is the rule for rounding after a calculation ?

  Round the result to three significant figures.
• What is the structure of an atom?

  Atoms have a positively charged nucleus surrounded by negatively charged electrons.
• Where are electrons located in an atom?

  Electrons are found around the nucleus in an electron cloud.
• What charge do protons have?

  Protons have a positive charge
• What is the mass and charge of neutrons?

  Neutrons have virtually the same mass as protons but no charge.
• What are the naming conventions for binary ionic compounds?

  • Cation is named first, then anion.
  • name of the element +( root + -ide)
  • Calcium chloride
• What is the formula for molar mass in relation to moles?

  mass (M) is calculated as M = Mm x n.
• How do you convert grams to atoms or particles?

  You first convert grams to moles, then to atoms or particles.
• How is mass composition calculated?

  Mass composition is calculated as % composition = (mass of element / total mass of compound) x 100.
• What is an empirical formula?

  An empirical formula represents the simplest whole-number ratio of elements in a compound,
• What is a molecular formula?


  A molecular formula shows the actual number of atoms of each element in a molecule
• How do you find the mass of a hydrate and its components?

  • Find the mass of the hydrate.
  • Find the mass of the anhydrous compound.
  • Find the mass of water.
  • Calculate the moles of water and anhydrous compound.
  • Determine the empirical formula indicating how much water is present.
• What does mass spectroscopy analysis involve?

  Mass spectroscopy analysis involves looking at the elements' mass on the periodic table and identifying the one with the closest mass.
• How do you calculate the average mass of isotopes in mass spectroscopy?

  You take each isotope's mass and multiply it by their percent abundance.
• mass composition

  Find mol of compound 

  Find mol of each element in compound

  X to get mass

  Then divide by mass of compound x 100
• empirical formula

  after % compostition

  Take smallest of all mole and divide all the moles
• Molecular formula

  Find the mass of the empirical formula 

  Divide molecular mass by mass of empirical formula

  Then times empirical formula by answer