Problem 44 - General Chemistry: Principles and Modern Applications

Question

Give an appropriate formula for each of the following compounds: (a) calcium sulfate dihydrate; (b) hydrosulfuric acid; (c) sodium hydrogen sulfate; (d) disulfuric acid.

Step-by-Step Solution

Answer

\(CaSO_4 \cdot 2H_2O\), \(H_2S\), \(NaHSO_4\), \(H_2S_2O_4\)

Step 1: Decipher Calcium Sulfate Dihydrate

This compound consists of calcium (Ca), sulfate (\(SO_4\)) and dihydrate, which implies two water molecules (\(H_2O\)). Hence the formula will be \(CaSO_4 \cdot 2H_2O\).

Step 2: Translate Hydrosulfuric Acid

Hydrosulfuric acid is made up of hydrogen and sulfide ion. The sulfide ion has a charge of -2 and hydrogen has +1. Hence there will be two hydrogen ions for each sulfide ion, making the formula \(H_2S\).

Step 3: Interpret Sodium Hydrogen Sulfate

This compound is composed of sodium (Na), hydrogen (H) and sulfate (\(SO_4\)). The resulting formula is \(NaHSO_4\).

Step 4: Uncover Disulfuric Acid

Disulfuric acid is an acid composed of two sulfur atoms (\(S_2\)), four oxygen atoms (\(O_4\)) and two hydrogen atoms (\(H_2\)). The formula for disulfuric acid will therefore be \(H_2S_2O_4\).

Key Concepts

Calcium Sulfate Dihydrate

Calcium sulfate dihydrate is a fascinating chemical compound that's commonly known as gypsum. This compound is widely used in construction, agriculture, and even in the medical field.
Calcium, represented as Ca, is a stable divalent metal, which means it typically forms a +2 charge. The sulfate ion is represented by the formula \(SO_4^{2-}\), indicating a -2 charge. Dihydrate implies the presence of two water molecules attached per formula unit of the compound. This means that calcium sulfate dihydrate's complete chemical formula is \(CaSO_4 \cdot 2H_2O\).
Key Points:

• Calcium forms a cation with a charge of +2.
• Sulfate is a polyatomic ion with a charge of -2.
• Dihydrate indicates two water molecules, so remember to add \(2H_2O\).

Understanding this compound's structure is not only important for chemistry, but it also provides insight into its various real-world applications.

Sodium Hydrogen Sulfate

When dealing with sodium hydrogen sulfate, it's essential to grasp its components: sodium, hydrogen, and sulfate. This compound often appears in detergents and is a critical part of many industrial processes.
Sodium (Na) is an alkali metal with a charge of +1. Hydrogen contributes a +1 charge as well, while the sulfate ion \(SO_4^{2-}\) brings a -2 charge into the mix. The chemical formula, therefore, is \(NaHSO_4\).
This combines the elements:

• Sodium (Na) with a +1 charge.
• Hydrogen (H) with a +1 charge.
• Sulfate (\(SO_4\)) with a -2 charge.

Knowing the correct combination of charges helps in understanding why the formula is \(NaHSO_4\), ensuring chemical stability.

Hydrosulfuric Acid

Hydrosulfuric acid might sound complex, but it's simply composed of hydrogen and sulfur, more commonly known as hydrogen sulfide. It’s an important compound found in nature, particularly in volcanic gases and some mineral waters.
In hydrosulfuric acid, hydrogen atoms bond with sulfur to create a compound with a straightforward formula: \(H_2S\). Here’s how that works:

• Hydrogen has a +1 charge.
• The sulfide ion has a -2 charge.

To balance the charges, two hydrogen atoms are required for one sulfide ion, resulting in the formula \(H_2S\).
This acid is also renowned for its distinctive rotten egg smell, a crucial identifier when handled in practical settings.

Disulfuric Acid

Disulfuric acid, also referred to as pyrosulfuric acid, is less commonly encountered but has significance in chemical processes such as the manufacturing of sulfonates.
This compound consists of two sulfur atoms, four oxygen atoms, and two hydrogen atoms, summarizing into the formula \(H_2S_2O_4\). It involves:

• Two hydrogen atoms (H).
• Two sulfur atoms (\(S_2\)).
• Four oxygen atoms (\(O_4\)).

The presence of these elements contributes to the formation of this unique chemical structure.
Understanding disulfuric acid's composition helps in studying its reactivity and use in complex chemical syntheses.