Percentage composition calculating, from formula

The percentage composition calculated from the empirical formula closely matches the given data. The formula is reasonable. [Pg.209]

Empirical formulae may also be calculated from percentage composition by mass in a similar way. [Pg.18]

In the problems above, the percentage data was calculated from the chemical formula, but the empirical formula can be determined if the percent compositions of the various elements are known. The empirical formula tells us what elements are present in the compound and the simplest whole-number ratio of elements. The data may be in terms of percentage, or mass, or even moles. But the procedure is still the same convert each to moles, divide each by the smallest number, then use an appropriate multiplier if needed. The empirical formula mass can then be calculated. If the actual molecular mass is known, dividing the molecular mass by the empirical formula mass gives an integer (rounded if needed) that is used to multiply each of the subscripts in the empirical formula. This gives the molecular (actual) formula, which tells which elements are in the compound and the actual number of each. [Pg.90]

Calculate the empirical formula of a compound from its mass percentage composition, Self-Test F.3. [Pg.87]

The approximate molar mass, calculated from the gas density data, is 89 g/mol. The empirical formula, calculated from the percentage composition data, is C2H3O with the empirical formula unit mass of 43.0. The exact molar mass must be (2)(43) = 86.0 g/mol since this is the only multiple of 43.0 (whole-number multiple) reasonably close to the approximate molecular formula of 89 g/mol. The molecule must be the equivalent of 2 empirical formulas CqHgO. [Pg.84]

Answer The first step is to calculate the empirical formula. To begin, we need to determine the number of moles of each element. However, the percentage composition does not tell us a mass. To get around this, the commonly used technique is to assume that you have a 100.0-gram sample of the substance. Because 100.0 grams is equal to 100%, you can simply take the percentages and say that the masses are equal to that same amount in grams. From there, the problem proceeds just like the previous example ... [Pg.274]

Calculating Percentage Composition from a Chemical Formula... [Pg.202]

In the previous Practice Problems, you used mass data to calculate percentage composition. This skill is useful for interpreting experimental data when the chemical formula is unknown. Often, however, the percentage composition is calculated from a known chemical formula. This is useful when you are interested in extracting a certain element from a compound. For example, many metals, such as iron and mercury, exist in mineral form. Mercury is most often found in nature as mercury(II) sulfide, HgS. Knowing the percentage composition of HgS helps a metallurgist predict the mass of mercury that can be extracted from a sample of HgS. [Pg.202]

When determining the percentage composition by mass of a homogeneous sample, the size of the sample does not matter. According to the law of definite proportions, there is a fixed proportion of each element in the compound, no matter how much of the compound you have. This means that you can choose a convenient sample size when calculating percentage composition from a formula. [Pg.202]

Sometimes there are more than two elements in a compound, or more than one atom of each element. This makes determining percentage composition more complex than in the example above. Work through the Sample Problem below to learn how to calculate the percentage composition of a compound from its molecular formula. [Pg.203]

In the previous section, you learned how to calculate the percentage composition of a compound from its chemical formula. Now you will do the reverse. You will use the percentage composition of a compound, along with the concept of the mole, to calculate the empirical formula of the compound. Since the percentage composition can often be determined by experiment, chemists use this calculation when they want to identify a compound. [Pg.208]

When determining the percentage composition of a compound from its formula, why do you base your calculations on a one mole sample ... [Pg.229]

Example of the Calculation of the Percentage Composition and the Empirical Formula, from the. Data of Analysis... [Pg.921]

Empirical Formula.—The calculation of the empirical formula from the percentage composition is as follows ... [Pg.922]

REVERSE CALCULATIONS PERCENTAGE COMPOSITION FROM FORMULA... [Pg.160]

Calculate percentage composition of a compound from its molecular formula or formula unit. [Pg.259]

If you know the chemical formula of any compound, then you can calculate the percentage composition. From the subscripts, you can determine the mass contributed by each element and add these to get the molar mass. Then, divide the mass of each element by the molar mass. Multiply by 100 to find the percentage composition of that element. [Pg.264]

The empirical formula of a compound can be simply related to the mass percentage of its constituent elements using the mole concept. For example, the empirical formula for ethylene (molecular formula C2H4) is CH2. Its composition by mass is calculated from the masses of carbon and hydrogen in 1 mol of CH2 formula units ... [Pg.35]

Calculation of the Atomic Formula. — In order to calculate the simplest formula of a substance from the figures giving its percentage composition, the method is as follows If a substance contains, e.g- -... [Pg.110]

We now know how to calculate the percentage composition of a compound, using information from a quantitative determination of its individual elements. This information may also be used to deduce the simplest formula for the compound. Example C.4 illustrates the approach that should be used to arrive at the simplest formula. [Pg.767]

The percentage composition result may be used to calculate the empirical formula of the substance being studied. Note that the empirical formula expresses the correct simplest whole-number ratios of the elements in the test substance. The empirical formula may not be the true, or molecular, formula of the substance being examined. The molecular formula may be some multiple of the empirical formula. The mathematical methods used to obtain the empirical formula are familiar from general chemistry. As an illustration, however, a sample calculation, using the same unknown sample that was presented earlier, is shown in Table 1.2. [Pg.2]

Just as the percentage composition by mass can be calculated from the formula of a compound, the simplest formula of a compound can be found from the percentage composition by mass of each element. The simplest formula is also known as the empirical formula. Here, empirical means obtained from experimental results . To find the simplest formula ... [Pg.125]

The simplest formula is not always the true or molecular formula it is only the simplest ratio of the atoms contained in the substance. If, for example, you calculated the simplest formula of hydrazine (N2H4) from its percentage composition by mass of nitrogen and hydrogen, you would obtain NH2. In order to establish the molecular formula, you need the molecular mass as well as the empirical formula. [Pg.126]

The empirical formula of an unknown compound can be worked out from its percentage composition using the calculations in Unit 8. [Pg.322]

In this experiment you will determine the empirical formula of a compound composed of lead and iodine. A weighed quantity of lead is reacted with nitric acid, HNO3, solution. The resulting lead nitrate solution is then reacted with sodium iodide, Nal, solution to form insoluble lead iodide, which is filtered, dried, and weighed. From your experimental data you can calculate the percentage composition and the ratio of moles of lead to moles of iodine in the compound, and then write the empirical formula. [Pg.63]

FIGURE 3.13 Procedure for calculating an empirical formula from percentage composition. The key step in the calculation is step 2, determining the number of moles of each element in the compound. [Pg.93]

Calculate the empirical and molecular formulas of a compound from percentage composition and molecular weight. (Section 3.5) Calculate amounts, in grams or moles, of reactants and products for a reaction. (Section 3.6)... [Pg.104]

A Figure 3.13 Procedure for calculating an empirical formula from percentage composition. [Pg.98]

Calculate the empirical and molecular formulas of a compound from percentage composition and molecular... [Pg.111]

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