Percentage composition from

Table 5.1 Mole percentage compositions from XPS study of the promoted iron catalyst used in ammonia synthesis171,172...

Calculating Percentage Composition from a Chemical Formula... 

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. 

REVERSE CALCULATIONS PERCENTAGE COMPOSITION FROM FORMULA... 

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. 

C.2 Determining Percentage Composition from Experimental Data... 

Caicuiating Percentage Composition from Experimentai Data... 

CALCULATION OF PERCENTAGE COMPOSITION FROM COMBUSTION DATA... 

To obtain the molecular formula of a substance, you need two pieces of information (1) as in the previous section, the percentage composition, from which the empirical formula can be determined and (2) the molecular weight The molecular weight allows you to choose the correct multiple of the empirical formula for the molecular formula. We will illustrate these steps in the next three examples. 

Calculating the percentage composition from the formula Given the formula of a compound, calculate the mass percentages of the elements in it. (EXAMPLE 3.7)... 

When a new substance is synthesized or is discovered, it is analyzed quantitatively to reveal its percentage composition. From these data, the empirical formula is then determined. An empirical formula consists of the symbols for the elements combined in a compound, with subscripts showing the smallest whole-number mole ratio of the different atoms in the compound. For an ionic compound, the formula unit is usually the compound s empirical formula. For a molecular compound, however, the empirical formula does not necessarily indicate the actual numbers of atoms present in each molecule. For example, the empirical formula of the gas diborane is BHg, but the molecular formula is BgHg. In this case, the number of atoms given by the molecular formula corresponds to the empirical ratio multiplied by two. 

A.4 (a) To calculate the percentage composition from the molecular formula, first determine the weight of each element in 1 mol of the compound. For C6H12O6,... 

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