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Relative atomic, isotopic, molecular and formula masses: Relative atomic mass: the weighted a... more Relative atomic, isotopic, molecular and formula masses: Relative atomic mass: the weighted average mass of the atoms of an element, taking into account the proportions of naturally occurring isotopes, measured on a scale on which an atom of the carbon-12 isotope has a mass of exactly 12 units. Relative formula mass: the mass of one formula unit of a compound measured on a scale on which an atom of the carbon-12 isotope has a mass of exactly 12 units. Relative isotopic mass: the mass of a particular isotope of an element on a scale in which an atom of the carbon-12 isotope has a mass of exactly 12 units. Relative molecular mass: the mass of a molecule measured on a scale in which an atom of the carbon-12 isotope has a mass of exactly 12 units. Mole and the Avogadro constant: One mole of a substance is the amount of that substance that has the same number of specific particles (atoms, molecules or ions) as there are atoms in exactly 12g of the carbon-12 isotope. The number of atoms in a mole of atom is 6.02×10 23 atoms. This number is called the Avogadro constant. The symbol for the Avogadro constant is L (or NA). Analyse mass spectra in terms of isotopic abundances: A mass spectrometer compares how much of each isotope is present-the relative abundance (isotopic abundance). The mass spectrum produced shows the relative abundance (isotopic abundance) on the vertical axis and the mass to ion charge ratio (m/e) on the horizontal axis. For single positively charged ions the m/e values give the nucleon number of the isotopes detected. Calculate the relative atomic mass of an element: To calculate the relative atomic mass: 1. Multiply each isotopic mass by its percentage abundance. 2. Add the figures together. 3. Divide by 100. ✽ Note: the number of significant figures should be consistent with the data given. Empirical and molecular formula: The empirical formula of a compound is the simplest whole number ratio of the elements present in one molecule or formula unit of the compound. The molecular formula of a compound shows the total number of atoms of each element present in a molecule. Perform calculations, including use of the mole concept, involving: One mole of a gas occupies 24 dm 3 at room temperature (25 ° C) and a pressure of 101 kPa (1 atm). Deduce stoichiometric relationships from calculations:
Relative atomic, isotopic, molecular and formula masses: Relative atomic mass: the weighted a... more Relative atomic, isotopic, molecular and formula masses: Relative atomic mass: the weighted average mass of the atoms of an element, taking into account the proportions of naturally occurring isotopes, measured on a scale on which an atom of the carbon-12 isotope has a mass of exactly 12 units. Relative formula mass: the mass of one formula unit of a compound measured on a scale on which an atom of the carbon-12 isotope has a mass of exactly 12 units. Relative isotopic mass: the mass of a particular isotope of an element on a scale in which an atom of the carbon-12 isotope has a mass of exactly 12 units. Relative molecular mass: the mass of a molecule measured on a scale in which an atom of the carbon-12 isotope has a mass of exactly 12 units. Mole and the Avogadro constant: One mole of a substance is the amount of that substance that has the same number of specific particles (atoms, molecules or ions) as there are atoms in exactly 12g of the carbon-12 isotope. The number of atoms in a mole of atom is 6.02×10 23 atoms. This number is called the Avogadro constant. The symbol for the Avogadro constant is L (or NA). Analyse mass spectra in terms of isotopic abundances: A mass spectrometer compares how much of each isotope is present-the relative abundance (isotopic abundance). The mass spectrum produced shows the relative abundance (isotopic abundance) on the vertical axis and the mass to ion charge ratio (m/e) on the horizontal axis. For single positively charged ions the m/e values give the nucleon number of the isotopes detected. Calculate the relative atomic mass of an element: To calculate the relative atomic mass: 1. Multiply each isotopic mass by its percentage abundance. 2. Add the figures together. 3. Divide by 100. ✽ Note: the number of significant figures should be consistent with the data given. Empirical and molecular formula: The empirical formula of a compound is the simplest whole number ratio of the elements present in one molecule or formula unit of the compound. The molecular formula of a compound shows the total number of atoms of each element present in a molecule. Perform calculations, including use of the mole concept, involving: One mole of a gas occupies 24 dm 3 at room temperature (25 ° C) and a pressure of 101 kPa (1 atm). Deduce stoichiometric relationships from calculations: