Chapter 2: Problem 95
Zinc metal ( \(2.50 \mathrm{g}\) ) combines with \(9.70 \mathrm{g}\) of iodine to produce zinc iodide, \(\mathrm{Zn}_{x} \mathrm{I}_{y}\). What is the formula of this ionic compound?
Short Answer
Expert verified
The formula of the compound is \( \text{ZnI}_2 \).
Step by step solution
01
Identify Moles of Zinc
First, we need to determine how many moles of zinc are present. The molar mass of zinc (Zn) is approximately 65.38 g/mol. Calculate the moles of zinc as follows: \[ \text{Moles of Zn} = \frac{2.50 \text{ g}}{65.38 \text{ g/mol}} = 0.0382 \text{ mol} \]
02
Identify Moles of Iodine
Next, calculate the moles of iodine. Iodine (I) exists as a diatomic molecule (I2). The molar mass of iodine (I2) is approximately 253.8 g/mol. Calculate the moles of iodine as follows: \[ \text{Moles of I}_2 = \frac{9.70 \text{ g}}{253.8 \text{ g/mol}} = 0.0382 \text{ mol} \]
03
Determine the Empirical Formula
Compare the moles of zinc to iodine. Both are approximately 0.0382 moles, suggesting a 1:1 mole ratio between Zn and Iā. However, keep in mind iodine is diatomic, so for the compound, each iodine unit splits into two iodide ions, meaning the empirical formula here is likely \( \text{ZnI}_2 \).
04
Conclude on the Chemical Formula
The chemical formula of the compound is derived from the simplest whole number ratio of the elements in the compound. Since we have determined a ratio of 1:2 (for iodide), the formula for zinc iodide becomes \( \text{ZnI}_2 \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Moles
The concept of moles is fundamental in understanding chemical reactions and formulas. The mole is a unit in chemistry used to express amounts of a chemical substance. One mole contains exactly 6.022 x 10\(^{23}\) elementary entities (such as atoms, molecules, or ions). This is known as Avogadro's number. Moles allow chemists to count atoms and molecules in a given sample by weighing them.
Here's why this is useful: Chemical reactions occur at the atomic level and these reactions are neither based on mass nor volume but on the number of particles themselves. Thus, using moles helps in communicating and calculating how reactions happen on a measurable scale.
When we calculate moles in a reaction, we use the formula:
\[ \text{Moles} = \frac{\text{Mass of substance (g)}}{\text{Molar mass (g/mol)}} \]
For instance, in the problem with zinc and iodine, we began by determining the moles present in each element to understand the base quantities involved in the chemical equation.
Here's why this is useful: Chemical reactions occur at the atomic level and these reactions are neither based on mass nor volume but on the number of particles themselves. Thus, using moles helps in communicating and calculating how reactions happen on a measurable scale.
When we calculate moles in a reaction, we use the formula:
\[ \text{Moles} = \frac{\text{Mass of substance (g)}}{\text{Molar mass (g/mol)}} \]
For instance, in the problem with zinc and iodine, we began by determining the moles present in each element to understand the base quantities involved in the chemical equation.
Empirical Formula
An empirical formula represents the simplest ratio of the elements in a compound. Unlike the molecular formula, it is not concerned with the actual number of atoms of each element, but rather their simplest form.
To determine the empirical formula, we need to convert the masses of individual elements in a compound into moles, and then find the simplest ratio of these moles. Oftentimes, we rely on finding the greatest common divisor to transform the mole ratio into whole numbers.
For example, in the determination of zinc iodide's empirical formula, we discovered that zinc and iodine were both approximately in a 1-to-1 mole ratio. However, because iodine is a diatomic molecule (\(I_2\)), this impacts how it binds in compounds. Each iodine molecule breaks down into two iodide ions in the reaction with zinc, leading to a 1:2 ratio (zinc:iodide) and resulting in the empirical formula \(\text{ZnI}_2\). This showcases the power of the empirical formula in simplifying and accurately representing compound structures.
Thus, empirical formulas play a pivotal role in summarizing the composition of ionic compounds concisely without the clutter of molecular specifics.
To determine the empirical formula, we need to convert the masses of individual elements in a compound into moles, and then find the simplest ratio of these moles. Oftentimes, we rely on finding the greatest common divisor to transform the mole ratio into whole numbers.
For example, in the determination of zinc iodide's empirical formula, we discovered that zinc and iodine were both approximately in a 1-to-1 mole ratio. However, because iodine is a diatomic molecule (\(I_2\)), this impacts how it binds in compounds. Each iodine molecule breaks down into two iodide ions in the reaction with zinc, leading to a 1:2 ratio (zinc:iodide) and resulting in the empirical formula \(\text{ZnI}_2\). This showcases the power of the empirical formula in simplifying and accurately representing compound structures.
Thus, empirical formulas play a pivotal role in summarizing the composition of ionic compounds concisely without the clutter of molecular specifics.
Ionic Compound
An ionic compound is made up of cations (positively charged ions) and anions (negatively charged ions). These compounds are neutral overall, but they are composed of charged ions which balance each other. The cations and anions form a distinct lattice structure, which gives ionic compounds their characteristic properties like high melting and boiling points.
Zinc iodide, \(\text{ZnI}_2\), is an ionic compound where zinc exists as \(\text{Zn}^{2+}\) and iodine as \(\text{I}^-\). In the reaction that combines zinc and iodine to form \(\text{ZnI}_2\), zinc donates two electrons, one to each iodide ion, resulting in a balanced ionic lattice where each \(\text{Zn}^{2+}\) is bonded with two \(\text{I}^-\) ions.
The formation of ionic compounds is driven by the desire of atoms to achieve a stable electron configuration. Metals generally lose electrons to become positive ions, while non-metals gain electrons to become negative ions. This electron transfer forms the strong electrostatic forces of attraction that hold ionic lattices together.
Understanding ionic compounds is essential when determining the chemical formula of compounds formed from different elements. It helps in predicting the number of each ion involved and ensures that when the compound is formed, it is electrically neutral.
Zinc iodide, \(\text{ZnI}_2\), is an ionic compound where zinc exists as \(\text{Zn}^{2+}\) and iodine as \(\text{I}^-\). In the reaction that combines zinc and iodine to form \(\text{ZnI}_2\), zinc donates two electrons, one to each iodide ion, resulting in a balanced ionic lattice where each \(\text{Zn}^{2+}\) is bonded with two \(\text{I}^-\) ions.
The formation of ionic compounds is driven by the desire of atoms to achieve a stable electron configuration. Metals generally lose electrons to become positive ions, while non-metals gain electrons to become negative ions. This electron transfer forms the strong electrostatic forces of attraction that hold ionic lattices together.
Understanding ionic compounds is essential when determining the chemical formula of compounds formed from different elements. It helps in predicting the number of each ion involved and ensures that when the compound is formed, it is electrically neutral.
