Compounds mass percent composition

The mass percent composition is a listing of the mass of each element present in 100 g of a compound. This percentage by mass listing is also called the compound s elemental analysis. 

We illustrate how the mass percent composition of a compound is related to its chemical formula using ammonium nitrate (NH4 NO3). The molar masses of NH4 NO3 and its constituent elements can be used to convert the chemical formula into mass percentages. 

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. 

C03-0081. Portland cement contains CaO, Si02, AI2 O3, and FC2 O3. Calculate the mass percent composition of each compound. 

B We use the same technique as before determine the mass of each element in a mole of the compound. Their sum is the molar mass of the compound. The percent composition is determined by comparing the mass of each element with the molar mass of the compound. 

Making particle numbers manageable with Avogadro s number Converting between masses, mole counts, and volumes Dissecting compounds with percent composition Moving from percent composition to empirical and molecular formulas... 

What is the empirical formula of stannous fluoride, the first fluoride compound added to toothpaste to protect teeth against decay Its mass percent composition is 24.25% F, 75.75% Sn. 

The data used to determine the chemical formula for a compound may be in the form of percent composition or it may be the actual masses of the elements in a given mass of the compound. If percent composition is given, you can assume that the total mass of the compound is 100.00 g and that the percent by mass of each element is equal to the mass of that element in grams. For example, the percent composition of an oxide of sulfiir is 40.05% S and 59.95% O. Thus, as you can see in Figure 11-10, 100.00 g of the oxide contains 40.05 g S and 59.95 g O. The mass of each element can be converted to a number of moles by multiplying by the inverse of the molar mass. Recall that the number of moles of S and O are calculated in this way. 

Percent composition or masses of the elements in a given mass of compound can be used to determine the formula for the compound. If percent composition is given, assume the total mass of the compound is... 

Percent means parts per 100 parts. Just as each piece of pie is a percent of the whole pie, each element in a compound is a percent of the whole compound. The percent composition of a compound is the mass percent of each element in the compound. The molar mass represents the total mass, or 100%, of the compound. Thus, the percent composition of water, H2O, is 11.19% H and 88.79% O by mass. According to the law of definite composition, the percent composition must be the same no matter what size sample is taken. 

Another way to express how much of an element is in a given compound is to use the element s mass percent composition for that compound. The mass percent composition or simply mass percent of an element is the element s percentage of the total mass of the compound. For example, the mass percent composition of sodium in sodium chloride is 39%. This information tells us that a 100-g sample of sodium chloride contains 39 g of sodium. The mass percent composition for a compound can be determined from experimental data using the formula ... 

In the previous section, we learned how to calculate mass percent composition from experimental data and how to use mass percent composition as a conversion factor. We can also calculate the mass percent of any element in a compound from the chemical formula for the compound. Based on the chemical formula, the mass... 

In Section 6.7, we learned how to calculate mass percent composition from a chemical formula. But can we go the other way Can we calculate a chemical formula from mass percent composition This is important because laboratory analyses of compounds do not often give chemical formulas directly rather, they give the relative masses of each element present in a compound. For example, if we decompose water into hydrogen and oxygen in the laboratory, we could measure the masses of hydrogen and oxygen produced. Can we determine a chemical formula for water from this kind of data ... 

We just learned how to go from the chemical formula of a compound to its mass percent composition. Can we also go the other way ... 

A compound with the following mass percent composition has a molar mass of 60.10 g/mol. Find its molecular formula. C 39.97% H 13.41% N 46.62%... 

Write down (or calculate) the masses of each element present in a sample of the compound. If you are given mass percent composition, assume a 100-g sample and calculate the masses of each element from the given percentages. 

Mass percent composition can be used as a conversion factor between grams of a constituent element and grams of the compound. Write the conversion factor (including units) inherent in each mass percent composition. 

What is the mathematical formula for calculating mass percent composition from a chemical formula How are the empirical formula and the molecular formula of a compound related ... 

Calculate the mass percent composition of nitrogen in each compound. (a) N2O (b) NO (c) NO2 (d) N2O5 80. Calculate the mass percent composition of carbon in each compound. (a) C2H2 (b) C3H6 (c) C2H6 (d) C2H6O... 

Determine the chemical formula of each compound and then refer to it to calculate the mass percent composition of each constituent element. 

In 1996, the media reported that possible evidence of life on Mars was found on a meteorite called Allan Hills 84001 (AH 84001). The meteorite was discovered in Antarctica in 1984 and is believed to have originated on Mars. Elemental analysis of substances within its crevices revealed carbon-containing compounds that normally derive only from living organisms. Suppose that one of those compounds had a molar mass of 202.23 g/mol and the mass percent composition C, 95.02% H, 4.98%. What is the molecular formula for the carbon-containing compound ... 

Because the atoms of the elements in a compound are combined in a definite proportion, they are also combined in a definite proportion by mass. Thus, when we know the mass of an element in a sample of a compound, we can calculate its mass percent composition or mass percent, which is the mass of an element divided by the total mass of the compound and multiplied by 100%. 

Given the formula of a compound, calculate the mass percent composition from the mass percent composition, determine the empirical formula of a compound. 

We can also calculate mass percent composition of a compound by using its molar mass. Then the total mass of each element is divided by the molar mass of the compound and multiphed by 100%. 

The odor of pears is due to the organic compound called propyl acetate, which has a formula of C5H10O2. What is its mass percent composition ... 

The organic compound ethylene glycol, C2H6O2, nsed as automobile antifreeze, is a sweet-tasting liquid, which is toxic to humans and animals. What is the mass percent composition of ethylene glycol ... 

The percent nitrogen depends on the type of nitrogen compound used in the fertilizer. The percent nitrogen by mass in each type is calculated using mass percent composition. 

Often, the mass percent of each element in a compound is given. The mass percent composition is true for any quantity of the compound. For example, methane, CH4, always has a mass percent composition of 74.9% C and 25.1% H. Thus, if we assume that we have a sample of exactly 100. g of the compound, we can determine the grams of each element in that 100. g sample as shown in Sample Problem 7.9. 

Sulfate of potash is the common name of a compound used in fertilizers to supply potassium and sulfur. What is the empirical formula of this compound if it has a mass percent composition of 44.9% K, 18.4% S, and 36.7% O ... 

The mass percent composition is obtained by dividing the mass in grams of one or aU elements in a compound by the mass of that compound... 

CI.9 Oxalic acid, an organic compound found in plants and vegetables such as rhubarb, has a mass percent composition of 26.7% C, 2.24% H, and 71.1% 0. Oxalic acid can interfere with respiration and cause kidney or bladder stones. If a large quantity of rhubarb leaves is ingested, the oxalic acid can be toxic. The lethal dose (LD50) in rats for oxalic acid is 375 mg/kg. Rhubarb leaves contain about 0.5% by mass of oxalic add. (2.7,7.4,7.5)... 

STRATEGIZE The molecular formula teUs you that there are 4 mol of Cl in each mole of Freon-112. Find the mass percent composition from the chemical formula by using the equation that defines mass percent. The conceptual plan shows you how to use the mass of Cl in 1 mol of C2CI4F2 and the molar mass of C2CI4F2 to find the mass percent of Cl. CONCEPTUAL PLAN, , 4 X molar mass Cl, Mass % Cl = X 100% molar mass C2CI4F2 RELATIONSHIPS USED mass of element X in 1 mol of compound Mass percent of element X — — X 100% mass of 1 mol of compound... 

The mass percent composition of an element in a compound is a conversion factor between mass of the element and mass of the compound. For example, we saw that the mass percent composition of Cl in CCI2F2 is 58.64%. Since percent means per hundred, there are 58.64 g Cl per hundred grams CCI2F2, which can be expressed as the ratio ... 

Notice that the mass percent composition acts as a conversion factor between grams of the compound and grams of the constituent element. To calculate grams Cl, we follow the conceptual plan. 

STRATE6IZE Convert between mass of a constituent element and mass of a compound by using mass percent composition as a conversion factor. 

Mass percent composition is one way to understand how much chlorine is in a particular chlorofluorocarbon or, more generally, how much of a constituent element is present in a given mass of any compound. However, we can also approach this type of problem in a different way. Chemical formulas contain within them inherent relationships between atoms (or moles of atoms) and molecules (or moles of molecules). For example, the formula for CCI2F2 teUs us that 1 mol of CCI2F2 contains 2 mol of Cl atoms. We write the ratio as ... 

With ratios such as these—which come from the chemical formula—we can directly determine the amounts of the constituent elements present in a given amount of a compound without having to calculate mass percent composition. For example, we calculate the number of moles of Cl in 38.5 mol of CCI2F2 as follows ... 

QIO. List the elements in the compound CF2CI2 in order of decreasing mass percent composition. 

---