Question

Calculate the formula mass for each of the following compounds: a. CO b. \(\mathrm{CO}_{2}\) c. \(\mathrm{C}_{6} \mathrm{H}_{14}\) d. \(\mathrm{HCl}\)

Short answer

Formula masses: a) CO: 28.01 amu, b) \(\mathrm{CO}_{2}\): 44.01 amu, c) \(\mathrm{C}_{6} \mathrm{H}_{14}\): 86.18 amu, d) HCl: 36.46 amu.

Step-by-step solution

Calculate the formula mass for CO

For CO, add the atomic mass of carbon (C), which is about 12.01 amu, to the atomic mass of oxygen (O), which is about 16.00 amu.

Calculate the formula mass for \(\mathrm{CO}_{2}\)

For \(\mathrm{CO}_{2}\), add the atomic mass of carbon (C) to twice the atomic mass of oxygen (O) since there are two oxygen atoms.

Calculate the formula mass for \(\mathrm{C}_{6} \mathrm{H}_{14}\)

For \(\mathrm{C}_{6} \mathrm{H}_{14}\), add the atomic mass of six carbon atoms and the atomic mass of fourteen hydrogen atoms. Carbon has an atomic mass of about 12.01 amu and hydrogen about 1.008 amu.

Calculate the formula mass for HCl

For HCl, add the atomic mass of hydrogen (H), which is about 1.008 amu, to the atomic mass of chlorine (Cl), which is about 35.45 amu.

Key concepts

Molar Mass

Understanding the concept of molar mass is essential for anyone delving into the realm of chemistry. Simply put, the molar mass is the weight of one mole of a substance, typically expressed in grams per mole (g/mol). This measurement tells us how much one mole of a particular element or compound weighs, which is crucial for converting between the amount of substance and its mass in many chemical reactions and equations.

For instance, when calculating the molar mass of a compound like carbon monoxide (CO), the molar masses of each constituent element are summed up. Considering the atomic mass of carbon is roughly 12.01 atomic mass units (amu) and oxygen is approximately 16.00 amu, we add these values to determine CO's molar mass. Since each mole of CO consists of one mole of carbon and one mole of oxygen, the molar mass can be calculated by directly combining their respective atomic weights.

Atomic Mass Unit

Diving further into the subject, the term atomic mass unit (amu) may frequently appear. It's a unit of mass used to express atomic and molecular weights. One amu is defined as one twelfth of the mass of a carbon-12 atom, and it's remarkably tiny—around 1.66053906660 x 10^-24 grams.

Understanding amu is vital for calculating the molar mass, as seen in the exercise example. Carbon has an atomic mass of approximately 12.01 amu and oxygen 16.00 amu. This unit allows scientists to use numbers that are more manageable when dealing with atoms and molecules, which are incredibly light and almost impossible to weigh on typical scales.

Moreover, when using atomic mass units, it's important to note that these are average values, as they account for the presence of different isotopes and their relative abundances.

Chemical Composition

Chemical composition, another key term in our chemistry journey, pertains to the identification and quantification of the elements that constitute a chemical compound. Knowing a compound's chemical composition is essential for calculating the formula mass, as it informs us of the types and numbers of atoms present. For example, \( \mathrm{C}_6 \mathrm{H}_{14} \) implies that there are six carbon atoms and fourteen hydrogen atoms in one molecule of hexane.

By understanding the chemical composition, we can deduce that to calculate the formula mass of hexane, we must sum up the molar masses of six carbon atoms and fourteen hydrogen atoms, considering their atomic mass units. The precision in these calculations is essential for accurately measuring reactants and products in a chemical reaction, as well as for predicting the properties of the compound.