Question Video: Writing Compound Names from Chemical Formulas | Nagwa Question Video: Writing Compound Names from Chemical Formulas | Nagwa

Question Video: Writing Compound Names from Chemical Formulas Chemistry • First Year of Secondary School

Which of the following is equivalent to the chemical formula “3CO₂”? [A] 3 free carbon atoms and 6 free oxygen atoms [B] 1 molecule of triple carbon dioxide [C] 3 carbon monoxide molecules [D] 3 dioxycarbon molecules [E] 3 molecules of carbon dioxide

03:31

Video Transcript

Which of the following is equivalent to the chemical formula three CO2? (A) Three free carbon atoms and six free oxygen atoms. (B) One molecule of triple carbon dioxide. (C) Three carbon monoxide molecules. (D) Three dioxycarbon molecules. Or (E) three molecules of carbon dioxide.

To answer this question, we first need to understand the components of a chemical formula. A chemical formula is an expression of chemical symbols and numerical subscripts that represent the composition of one unit of a compound. So let’s take a closer look at the chemical formula CO2. In this formula, we see a capital C and a capital O. These are the chemical symbols of carbon and oxygen.

Following the chemical symbol of oxygen, we see a subscript two. A subscript after a chemical symbol tells us the number of atoms of that element in one unit of a compound. No subscript appears after the chemical symbol of carbon. This means that one unit of this compound only contains one atom of carbon.

We now know that one unit of this compound contains one atom of carbon and two atoms of oxygen. But what type of compound is CO2 and what is its chemical name? Both carbon and oxygen are nonmetals. When atoms of two nonmetals form a compound, the type of compound is a binary molecular compound, which consists of atoms of two different elements, which are covalently bonded together.

So we now know that the carbon and oxygen atoms are covalently bonded together to form one molecule. We can name this binary molecular compound by writing the name of the first element in the chemical formula. The first element in the formula is carbon. Next, we write the root of the second element’s name, followed by the suffix I-D-E. The root of the word “oxygen” is “ox,” to which we’ll add the suffix I-D-E. Finally, we’ll add Greek prefixes in front of each word to indicate the number of atoms of each element in the compound. But if there is only one of the first element listed in the name, we won’t use the prefix mono-.

There is only one carbon atom, so we won’t add a prefix to the word “carbon.” But there are two oxygen atoms, so we need to add the prefix di- in front of the word “oxide.” So now we know that CO2 is a molecule which contains one atom of carbon and two atoms of oxygen and has the name carbon dioxide.

The last thing we need to account for is the three written in front of CO2. Numbers written in front of a chemical formula are called coefficients. Coefficients are used to indicate the number of discrete units, either molecules or formula units, depending on the type of compound. So placing a three in front of the chemical formula CO2 indicates that there are three molecules of carbon dioxide. From this, we can determine that the correct answer is answer choice (E). The chemical formula three CO2 is equivalent to three molecules of carbon dioxide, answer choice (E).

Join Nagwa Classes

Attend live sessions on Nagwa Classes to boost your learning with guidance and advice from an expert teacher!

  • Interactive Sessions
  • Chat & Messaging
  • Realistic Exam Questions

Nagwa uses cookies to ensure you get the best experience on our website. Learn more about our Privacy Policy