Formula, calculating percentage composition

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]

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

We can turn this sort of calculation around and convert chemical formula into percentage composition. [Pg.160]

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

Chemical formulas can be used to calculate percentage composition. [Pg.268]

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]

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

The easiest way to calculate an empirical formula from percentage composition is to consider a 100.00 g sample of the compound. In this case, a 100.00 g sample would contain 62.04 g of carbon, 10.41 g of hydrogen, and 27.55 g of oxygen. Convert each mass to moles so that you can compare the mole ratio of the three elements. [Pg.698]

Self-TfsT F.4B The mass percentage composition of the compound thionyl difluoride is 18.59% O, 37.25% S, and 44.16% F. Calculate its empirical formula. [Pg.73]

The elemental analysis of a compound is usually determined by a laboratory that specializes in this technique. A chemist who has prepared a new compound sends a sample to the laboratory for analysis. The laboratory charges a fee that depends on the type and number of elements analyzed. The results are returned to the chemist as a listing of mass percent composition. The chemist must then figure out which chemical formula matches this composition. If a chemist has reason to expect a particular chemical formula, the observed percentages can be matched against the calculated percentages for the expected formula. This process is illustrated in Example 3-13. [Pg.156]

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

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

The table shows the values u0 for various percentage compositions of mixtures of CO with air, calculated according to the formula of the theory of flame propagation [5]... [Pg.282]

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]

If you assume that you have one mole of a compound, you can use the molar mass of the compound, with its chemical formula, to calculate its percentage composition. For example, suppose that you want to find the... [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]

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

In practice, you can determine a compound s empirical formula by analyzing its percentage composition. There are several different ways to do this. One way is to use a synthesis reaction in which a sample of an element with a known mass reacts with another element to form a compound. Since you know the mass of one of the elements and you can measure the mass of the compound produced, you can calculate the percentage composition. [Pg.211]

In section 6.2, you learned how to calculate the empirical formula of a compound based on percentage composition data obtained by experiment. In section 6.3, you will learn how chemists use the empirical formula of a compound and its molar mass to determine the molecular formula of a compound. [Pg.214]

You have learned how to calculate the percentage composition of a compound using its formula. Often, however, the formula of a compound is not known. Chemists must determine the percentage composition and molar mass of an unknown compound through experimentation. [Pg.219]

A 0.539 g sample of a compound that contained only carbon and hydrogen was subjected to combustion analysis. The combustion produced 1.64 g of carbon dioxide and 0.807 g of water. Calculate the percentage composition and the empirical formula of the sample. [Pg.221]

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

By this method it is possible to calculate the percentage composition of any compound, if its formula is known. [Pg.148]

Calculate the simplest formula of the compounds which have the indicated percentage composition, and give the name of the compound —... [Pg.156]

Calculate the molecular formula of the compounds having the Indicated percentage composition and vapor density —... [Pg.156]

Calculate the formula of a substance having the percentage composition —... [Pg.188]

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