Using the mass and length of the long piece of magnesium, the average mass of a 3 cm length can be calculated with sufficient accuracy. If a balance weighing to 0.001 g is not available, reasonable results could be obtained by weighing a much longer (eg 30 cm) piece of magnesium ribbon beforehand on a balance weighing to 0.01 g, measuring its length and then cutting it accurately into 3 cm lengths.Refer to CLEAPSS Laboratory Handbook Section 10.10.1. Ensure the burette taps are free from leakage, operate smoothly and are secure in their sockets. Access to room temperature and pressure measurements (see note 3).Access to a top-pan balance, accurate to +/– 0.001 g (see note 2).Including the time taken by the teacher to demonstrate the procedure, and allowing an average of five minutes for each student to weigh their magnesium ribbon, a total of 45 minutes should be adequate for the class to obtain and record their results. Timing will depend on the adequacy of access to top-pan balances, and the skill with which students can use the balance to sufficient accuracy. This is a class experiment suitable for students who already have a reasonable understanding of the mole concept, and are at least beginning to use chemical equations to perform calculations. From this, students can deduce the relative atomic mass of magnesium. They can then use the measured volume of hydrogen gas produced and the mass of magnesium to calculate the mass of magnesium required to produce one mole of hydrogen molecules. In this experiment, students react magnesium ribbon with dilute hydrochloric acid to produce hydrogen gas. RSC Yusuf Hamied Inspirational Science Programme.Introductory maths for higher education.The physics of restoration and conservation.Symbols, abbreviations, or full names for units of length,Īrea, mass, pressure, and other types. You can find metric conversion tables for SI units, as wellĪs English units, currency, and other data. The formula weight is simply the weight in atomic mass units of all the atoms in a given formula.Ĭonversion calculator for all types of measurement units. When calculating molecular weight of a chemical compound, it tells us how many grams are in one mole of that substance. Using the chemical formula of the compound and the periodic table of elements, we can add up the atomic weights and calculate molecular weight of the substance.įinding molar mass starts with units of grams per mole (g/mol). For bulk stoichiometric calculations, we are usually determining molar mass, which may also be called standard atomic weight or average atomic mass. This is not the same as molecular mass, which is the mass of a single molecule of well-defined isotopes. This is how to calculate molar mass (average molecular weight), which is based on isotropically weighted averages. The atomic weights used on this site come from NIST, the National Institute of Standards and Technology. These relative weights computed from the chemical equation are sometimes called equation weights. This site explains how to find molar mass.įormula weights are especially useful in determining the relative weights of reagents and products in a chemical reaction. The reason is that the molar mass of the substance affects the conversion. To complete this calculation, you have to know what substance you are trying to convert. The percentage by weight of any atom or group of atoms in a compound can be computed by dividing the total weight of the atom (or group of atoms) in the formula by the formula weight and multiplying by 100.Ī common request on this site is to convert grams to moles. If the formula used in calculating molar mass is the molecular formula, the formula weight computed is the molecular weight. In chemistry, the formula weight is a quantity computed by multiplying the atomic weight (in atomic mass units) of each element in a chemical formula by the number of atoms of that element present in the formula, then adding all of these products together. Grams Magnesium to moles, or enter other units to convert below: Enter two units to convert From: You can do the reverse unit conversion from
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