In organic chemistry, dry distillation of calcium formate Ca(HCOO)2 gives which main organic product?

Introduction / Context:
Dry distillation of calcium salts of carboxylic acids is a classic reaction in basic organic chemistry. Different calcium salts give different organic products when heated strongly without any liquid solvent. Calcium formate, Ca(HCOO)2, is the calcium salt of formic acid. This question tests whether you remember the specific product obtained when calcium formate is subjected to dry distillation, a reaction that is often used in textbooks to illustrate thermal decomposition of salts and the formation of aldehydes.

Given Data / Assumptions:

• The starting compound is calcium formate, Ca(HCOO)2.
• Dry distillation means strong heating of the solid without any added solvent.
• The options include several possible organic products: formic acid, acetic acid, formaldehyde and acetaldehyde, plus methanol as a plausible alcohol.
• We assume typical school level reaction conditions used to show decomposition of calcium formate.

Concept / Approach:
When calcium formate is heated strongly, it decomposes to give formaldehyde, calcium carbonate and hydrogen gas. The key point is that the formate ion HCOO minus is closely related to the aldehyde group. During dry distillation, the formate anion is converted into formaldehyde, HCHO, which is the simplest aldehyde. Acetic acid and acetaldehyde are formed from salts of acetic acid or other higher carboxylic acids, not from calcium formate. Formic acid itself is unstable on heating and does not distil unchanged in this reaction. Therefore, we look for the option that names formaldehyde as the main organic product.

Step-by-Step Solution:
Step 1: Recall that calcium salts of carboxylic acids can give characteristic products when heated. Step 2: For calcium formate, Ca(HCOO)2, the formate ion is the conjugate base of formic acid, the simplest carboxylic acid. Step 3: On dry distillation, calcium formate decomposes to produce formaldehyde (HCHO), calcium carbonate (CaCO3) and hydrogen gas (H2). Step 4: The main organic product that can be collected as a volatile compound is formaldehyde, HCHO. Step 5: Compare this with the options and select the one that names formaldehyde as the product.

Verification / Alternative check:
Many introductory organic chemistry books state this reaction in a word equation such as calcium formate on dry distillation gives formaldehyde, calcium carbonate and hydrogen. Balanced equations show that the carbon in the formate ion becomes the carbonyl carbon in formaldehyde. In the laboratory, the gas mixture evolved contains formaldehyde vapours that can be detected by their characteristic strong, irritating odour and reducing behaviour. There is no evidence that acetic acid or acetaldehyde is formed directly from calcium formate under these simple dry distillation conditions, which confirms that formaldehyde is the correct product to choose.

Why Other Options Are Wrong:
Option A, formic acid, is not the main product because the reaction involves decomposition of the formate salt rather than simple liberation of the acid. Option B, acetic acid, would be expected from calcium acetate, not calcium formate. Option D, acetaldehyde, is usually formed by reactions involving higher carboxylates or oxidation of ethanol, and not by dry distillation of calcium formate. Option E, methanol, is an alcohol and does not match the typical aldehyde product of this decomposition. Only option C correctly identifies formaldehyde (HCHO) as the main organic product of dry distillation of calcium formate.

Common Pitfalls:
Students often confuse formic acid and formaldehyde because their names sound similar and both contain one carbon atom. Another common mistake is to assume that any salt of a carboxylic acid will regenerate the same acid on heating, which is not true for calcium formate. It is helpful to remember that formate is closely linked to the aldehyde group and that calcium formate is a textbook example of thermal decomposition to formaldehyde. Keeping the specific association between each calcium salt and its decomposition product in mind will prevent confusion in similar questions.

Final Answer:
Dry distillation of calcium formate Ca(HCOO)2 gives Formaldehyde (HCHO) as the main organic product, along with inorganic by products such as calcium carbonate and hydrogen gas.