Question

A solid white substance A is heated strongly in the absence of air. It decomposes to form a new white substance \(B\) and a gas C.The gas has exactly the same properties as the product obtained when carbon is burned in an excess of oxygen. Based on these observations, can we determine whether solids \(\mathrm{A}\) and \(\mathrm{B}\) and gas \(\mathrm{C}\) are elements or compounds?

Short answer

Based on the given information, gas C (carbon dioxide) is a compound, as it is composed of one carbon atom and two oxygen atoms. Solid A is likely a compound containing carbon and oxygen, since it decomposes into solid B and gas C when heated. However, solid B could be either an element or a compound, as there is not enough information to definitively determine its nature.

Step-by-step solution

Identify the properties of gas C

Since gas C has the same properties as the product obtained when carbon is burned in excess oxygen, we can infer that gas C is carbon dioxide (CO2). Carbon dioxide is produced when carbon reacts with oxygen according to the following chemical equation: \[C + O_2 \rightarrow CO_2\]

Determine if gas C is an element or compound

Gas C, which is carbon dioxide (CO2), is a compound. A compound consists of two or more elements that are chemically combined in a fixed ratio. In the case of carbon dioxide, it is composed of one carbon atom and two oxygen atoms, representing a fixed combination of these two elements.

Identify the possible properties of solid A and solid B

We do not have enough information about solid A or solid B to definitively determine whether they are elements or compounds based solely on their color. However, we do know that when heated, solid A decomposes into solid B and a gas C (CO2). This indicates that solid A contains both carbon and oxygen, while solid B is a product resulted from a loss of oxygen and carbon in the form of CO2.

Determine if solid A and solid B are elements or compounds

Since solid A contains both carbon and oxygen, it is very likely that solid A is a compound. However, solid B could potentially be either a compound or an element, since we do not have enough information to make a definite determination. In conclusion, based on the given information, gas C is a compound (carbon dioxide), solid A is likely a compound (containing carbon and oxygen), and solid B could be either an element or compound with the given information.

Key concepts

Decomposition Reaction

A decomposition reaction is a type of chemical reaction where one substance breaks down into two or more simpler substances when energy is applied. This energy can often be in the form of heat, light, or electricity.
In the context of the exercise, the solid white substance A decomposes upon heating to produce a new white substance B and a gas C.
Since this process results in the separation of components, it's a perfect example of a decomposition reaction, where complex molecules are broken down into simpler atoms or molecules. Common examples include the decomposition of water into hydrogen and oxygen and the breakdown of hydrogen peroxide into water and oxygen.

• Decomposition reactions are usually endothermic, meaning they absorb heat.
• They often require a catalyst or heat to initiate the process.
• They result in the increase of the number of products from one reactant.

Understanding decomposition reactions helps in identifying whether the substances involved could be elements or compounds since the products result from the breakdown of the reactant.

Carbon Dioxide

Carbon dioxide is a compound consisting of one carbon atom and two oxygen atoms. The formation of carbon dioxide occurs when carbon combusts in the presence of oxygen, according to the reaction:
\[C + O_2 \rightarrow CO_2\]
This compound is colorless and odorless and plays a crucial role in the Earth's carbon cycle. Carbon dioxide is also a greenhouse gas, contributing to the Earth's warming by trapping heat within the atmosphere.
In our original exercise, gas C was identified as carbon dioxide due to its properties matching the gas produced from carbon burned in excess oxygen.

• It is crucial for photosynthesis in plants, converting it into oxygen.
• It's used in carbonated beverages to provide the fizz.
• It's heavier than air, which can affect its behavior in various environments.

Knowing that gas C is carbon dioxide allows us to conclude it is a compound, as it combines different elements—carbon and oxygen.

Compounds and Elements

Compounds and elements are the fundamental building blocks in chemistry, defining whether a substance is simple or complex.
An **element** is a pure substance that consists of only one type of atom. These are the simplest substances and cannot be broken down into simpler chemicals.
**Compounds**, on the other hand, are formed when two or more elements chemically bond in fixed proportions. For instance, water (H\(_2\)O) is a compound made from hydrogen and oxygen.
In our exercise:

• Solid A is likely a compound since it decomposes to form gas carbon dioxide and solid B.
• Gas C is identified as carbon dioxide, a well-known compound.
• Solid B needs more information to be classified, but it results from the decomposition of a more complex material, indicating it could be either.

Understanding the difference helps to categorize substances based on their chemical composition and decomposition behaviors.