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kg mol-1. Example. Calculate the number of moles of oxygen molecules in 4g. oxygen molecules have the formula O2 the relative mass will be 2 x 16 = 32 so the molar mass will be 32g mol-1. moles = mass.
Revision notes on 6.6.2 Kinetic Theory of Gases Equation for the AQA A Level Physics syllabus, written by the Physics experts at Save My Exams.
Use the ideal gas law to calculate pressure change, temperature change, volume change, or the number of molecules or moles in a given volume. Use Avogadro’s number to convert between number of molecules and number of moles.
The formula mass of a substance is the sum of the average atomic masses of each atom represented in the chemical formula and is expressed in atomic mass units. The formula mass of a covalent compound is also called the molecular mass. A convenient amount unit for expressing very large numbers of atoms or molecules is the mole.
Examples for elements and compounds are given in the table below, along with its formula, relative formula mass (RFM) and the mass of 1 mole.
Write a balanced equation for the decomposition of ammonium nitrate to form molecular nitrogen, molecular oxygen, and water. (Hint: Balance oxygen last, since it is present in more than one molecule on the right side of the equation.) Answer \[\ce{2NH4NO3 \rightarrow 2N2 + O2 + 4H2O} \nonumber \]
Answer. Empirical formula = H 2 O. Worked example. Substance X was analysed and found to contain 31.58% carbon, 5.26% hydrogen and 63.16% oxygen by mass. What is the empirical formula of substance X? Relative atomic masses, Ar: C = 12; H = 1; O = 16. Answer. Empirical formula = C 2 H 4 O 3. Examiner Tip. The molar ratio must be a whole number.
