The volume of gas can be found by means of several formulas. It is necessary to choose suitable, proceeding from the sizes given in a statement of the problem. The large role at selection of a necessary formula is played by environmental conditions, and in particular: pressure and temperature.
Instruction
1. Formula which is most often found in tasks: V = n*Vm, where V – the volume of gas (l), n – amount of substance (mol), Vm - the molar volume of gas (l/mol), under normal conditions (N at.) is standard size and it is equal to 22.4 l/mol. Happens so that in a condition there is no amount of substance, but there is a mass of a certain substance, then act this way: n = m/M where m is the mass of substance (g), M – the molar mass of substance (g/mol). We find molar weight according to D.I. Mendeleyev's table: under each element its atomic mass is written, we put all masses and we receive necessary for us. But such tasks meet quite seldom, usually in tasks there is a reaction equation. The solution of such tasks after it changes a little. Let's consider on an example.
2. What volume of hydrogen will be allocated under normal conditions if to dissolve aluminum weighing 10.8 g a lot of hydrochloric acid. We write down the reaction equation: 2Al + 6HCl (log huts.) = 2AlCl3 + 3H2. We solve a problem about this equation. We find amount of substance of aluminum which reacted: n(Al) = m(Al)/M (Al). To substitute data in this formula, we need to count the molar mass of aluminum: M (Al) = 27 g/mol. We substitute: n(Al) = 10.8/27 = 0.4 mol. From the equation we see that at dissolution of 2 mol of aluminum 3 mol of hydrogen are formed. We calculate what amount of substance of hydrogen it is formed of 0.4 mol of aluminum: n(H2) = 3*0.4/2 = 0.6 mol. Then we substitute data in a formula on finding of volume of hydrogen: V = n*Vm = 0.6*22.4 = 13.44 l. Here we also received the answer.
3. If we deal with a gas system, then such formula takes place: q(x) = V (x)/V, where q(x) (fi) – a volume fraction of a component, V (x) – the volume of a component (l), V – the volume of system (l). For finding of volume of a component we receive a formula: V (x) = q(x) * V. And if it is necessary to find system volume, then: V = V (x)/q (x).