Question

61\. Which of the following best describes the substance \(\mathrm{XeF}_{4}\) ? a. element b. compound c. heterogeneous mixture d. homogeneous mixture

Short answer

XeF4 is a substance formed by the chemical combination of Xenon (Xe) and Fluorine (F) in definite proportions by mass (1:4 ratio). It is not an element, as it contains more than one type of element, and it is not a mixture, as it is a single substance formed from a chemical combination. Therefore, XeF4 best fits the definition of a compound.

Step-by-step solution

Identify the components of the substance

The given substance, XeF4, has two components: Xenon (Xe) and Fluorine (F).

Consider the definition of an element

An element is a pure substance that cannot be broken down into simpler substances by chemical reactions. Xenon and Fluorine are both elements, but since XeF4 contains more than one type of element, it cannot be an element itself.

Consider the definition of a compound

A compound is a substance formed by the chemical combination of two or more elements in definite proportions by mass. In XeF4, Xenon and Fluorine chemically combine in a ratio of 1:4 (one Xenon atom to four Fluorine atoms). Therefore, XeF4 fits the definition of a compound.

Consider the definitions of homogeneous and heterogeneous mixtures

A homogeneous mixture is a mixture with a uniform composition and a single phase, while a heterogeneous mixture is a mixture with a non-uniform composition and multiple phases. XeF4 is not a mixture, as it is a single substance formed from the chemical combination of Xenon and Fluorine.

Choose the best description for XeF4

Based on our analysis above, XeF4 best fits the definition of a compound. Therefore, the correct answer is (b) compound.

Key concepts

Chemical Elements

When you hear about chemical elements, think of them as the fundamental building blocks of matter. These are pure substances that cannot be broken down into simpler substances through chemical reactions. The periodic table is like a directory of these elemental building blocks, listing them all out, each with unique properties like atomic number and symbol.

The world around you is made up of about 118 different elements. Some examples of elements include oxygen (O), carbon (C), and hydrogen (H). Each element is distinguished by the number of protons in its nucleus, resulting in that unique atomic number I mentioned before. This gives each element its own set of characteristics. For instance, gold is a shiny, yellow element that remains largely unreacted with other substances due to its low reactivity, which makes it valuable in jewelry and electronics.

When we look at the substance XeF₄, remember, it's not an element but a combination of two elements, xenon (Xe) and fluorine (F). Although elements alone have their unique identities, when they combine, they create something with entirely new properties.

Homogeneous Mixtures

Moving on to homogeneous mixtures, these are mixes of two or more substances that blend so thoroughly, you can't tell the components apart. Take a pinch of salt, stir it into a glass of water, and voilà, you've got a homogeneous mixture! Once the salt is dissolved, the resulting solution is uniform all the way through, meaning you get the same taste of saltiness in every sip.

In the kitchen, when you mix sugar into coffee, the sugar dissolves and you cannot see it anymore. Same goes for air — it's a mixture of gases like nitrogen, oxygen, and others, all perfectly blended so that each breath you take is consistent. Unlike a compound, the proportions of substances in a mixture can vary. You can have a lot of sugar or a little in your coffee, and it's still a homogeneous mixture.

In our textbook problem, XeF₄ isn't a homogeneous mixture. It's a pure substance where different elements are chemically bonded in fixed ratios; you won't find varying amounts of xenon or fluorine in different samples of XeF₄.

Heterogeneous Mixtures

The last concept to tackle is heterogeneous mixtures. These mixtures have an inconsistent composition; they're patchy. Imagine tossing different colored marbles into a bowl or making a salad with lettuce, tomatoes, and cucumbers. Each bite might give you a different taste or texture — that's what makes it heterogeneous.

Think of oil and water; even if you stir them vigorously, they eventually separate. A bowl of cereal is another everyday example. You can see and pick out the individual pieces of cereal from the milk. These mixtures are not uniform throughout, and their different components can often be manually separated by methods like filtration or decanting.

XeF₄, on the other hand, has a uniform chemical structure and cannot be separated into its components by physical means, contrasting with the very nature of heterogeneous mixtures. Thus, XeF₄ doesn't belong to this category either in our textbook exercise.