Editing Molecular Formula Notes
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<center><b>Molecular Formula Notes</b></center><br> Definition:<br> <br> What does it mean?<br> <Br> When do you have Molecular formula:<br> <br> <br> <u>Step to Calculate Molecular Formula</u><br> 1. Change mass percent (%) to actual masses or use given masses directly<br> *<b>Assume the mass of one mole of the compound <u>NOT 100.g compound (cpd)</u></b>. If you assume 100g, you will determine the empirical formula instead. 2. Change mass of element to mole of element<br> 3. Since you assumed mass of one mole of cpd, the moles should be close enough to whole to assume they are whole. So you do not have change to a molar ratio or multiple by a common number.<br> *Take smaller mole number and divide this number into all other mole number.<br> <br> <u>Step to Calculate Molecular Formula (MF) from Empirical Formula (EF)</u><br> As you know, molecular formula are really a certain number of "empirical formula" units. An analogue is a chain with several links. The chain is made up of several identical links so if you know the mass of the chain and the mass of a single link, then you can determine how many links there are in the chain. Similarly, the MF is made up of a certain number of EF units. Therefore, if you know the mass of the molecular formula (we call molar mass) and mass of a mole of the EF, if you divide the two, you get how many EF units there are in the MF. <br> 1. Determine the molar mass of the EF (you have to be given this or given the chemical formula of the EF).<br> 2. Must be given the molar mass of the MF.<br> 3. Divide the molar mass of the EF into the molar mass of the MF or <br> <u>MM of MF</u> = # of EF units in MF<br> MM of EF 4. Then multiple the subscripts in the EF with the # of EF in the MF to determine the correct subscript for the chemical formula for the MF. --------------<br> <b>Example When Give Actual Mass or Mass Percent Information and Asked for Both EF and MF.</b><br> <br> What is the EF and MF of a compound that is 94.2% oxygen and rest hydrogen? The molar mass of the compound is 34.0g/mole.<br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <b>Example of MF Calculation when given Molar Mass and EF of compound.</b><br> <br> What is Molecular Formula of a compound that has a molar mass of 342g/mole and has an Empirical Formula of Co<sub>1</sub>C<sub>4</sub>O<sub>4</sub><br><br><br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br>
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