Glycine is an amino acid made up of carbon, hydrogen, oxygen, and nitrogen atoms. Combustion of a \(0.2036\) -g sample gives \(132.9 \mathrm{~mL}\) of \(\mathrm{CO}_{2}\) at \(25^{\circ} \mathrm{C}\) and \(1.00 \mathrm{~atm}\) and \(0.122 \mathrm{~g}\) of water. What are the percentages of carbon and hydrogen in glycine? Another sample of glycine weighing \(0.2500 \mathrm{~g}\) is treated in such a way that all the nitrogen atoms are converted to \(\mathrm{N}_{2}(g)\). This gas has a volume of \(40.8 \mathrm{~mL}\) at \(25^{\circ} \mathrm{C}\) and \(1.00 \mathrm{~atm}\). What is the percentage of nitrogen in glycine? What is the percentage of oxygen? What is the empirical formula of glycine?

Combustion analysis is a laboratory method used to determine the elemental composition of a substance. In chemistry, this technique is especially crucial for identifying the amounts of carbon, hydrogen, and sometimes nitrogen in organic compounds. During combustion analysis, a sample is burned in excess oxygen, and the products, typically CO2 and H2O, are measured. From these measurements, one can calculate the amounts of carbon and hydrogen in the original sample.
Using the ideal gas law, chemists can convert the volumes of gaseous products collected during the experiment to moles, which then help to establish the ratios of the elements within the compound. In the example of glycine, the combustion analysis provided the necessary data to calculate moles of CO2 and H2O, and subsequently the mass and percentage composition of carbon and hydrogen in the amino acid. Careful analysis of the combustion products is a key step to ensure accurate empirical formula determination.

The ideal gas law is represented by the equation PV=nRT, which relates the pressure (P), volume (V), and temperature (T) of a gas to the number of moles (n) of the gas present, with R being the ideal gas constant. It's a fundamental equation in chemistry for studying gas-phase reactions and properties.

• P (Pressure) is typically measured in atmospheres (atm) or pascals (Pa).
• V (Volume) is measured in liters (L) or cubic meters (m^3).
• n (Moles) of the gas represents the quantity of the substance.
• R (Ideal Gas Constant) is 0.08206 L atm/(mol K) when using atm and L.
• T (Temperature) must be expressed in Kelvin (K) for the equation to work properly.

In the context of glycine's analysis, applying the ideal gas law allowed for the conversion of the measured volume of gases to moles, which is a critical step for the empirical formula determination. It's important to accurately measure the temperature and pressure during the combustion to use this law effectively.

Molar mass is the mass of one mole of a substance, usually expressed in grams per mole (g/mol). It numerically equals the average atomic or molecular mass of the substance. The molar mass allows chemists to convert between grams of substance and moles, a key conversion in stoichiometry and reaction calculations.
For instance, the molar mass of water (H2O) is approximately 18 g/mol because it has two hydrogen atoms (approx. 1 g/mol each) and one oxygen atom (approx. 16 g/mol). Hence, if a combustion reaction yields 0.122 g of water, dividing this mass by the molar mass of water would provide the number of moles of water produced. These moles can then be used to calculate the moles of hydrogen present. This concept is foundational when computing the proportion of elements in an empirical formula, as each element's contribution is based on its molar mass.

Percent composition gives the mass percentage of each element in a compound. It's essential for determining the empirical formula, where the lowest whole-number ratio of elements in a compound is established. To find the percent composition, you divide the mass of each element in a compound by the total mass of the compound, then multiply by 100 to get a percentage.

Importance of Accuracy

When performing these calculations, it's imperative to use accurate masses for all reactants and products to ensure the percent composition is correct. In the case of glycine, after determining the mass of carbon, hydrogen, and nitrogen by combustion analysis and ideal gas law calculations, dividing these masses by the total mass of the glycine sample and multiplying by 100 gave us the respective percentages. Knowing the percent composition of each element then leads to the ability to calculate the empirical formula, which summarizes the types and ratios of atoms in the simplest form.
In conclusion, the combined understanding of these concepts allows for comprehensive analysis of chemical compounds, showing how empirical formulas are derived from experimental data.