Which of the following acid is used by goldsmiths for cleaning gold and silver ornaments?

Options

A. HCI
B. `H_2 SO_4`
C. `HNO_3`
D. `H_3 PO_4`

Explanation

To determine which acid is used by goldsmiths for cleaning gold and silver ornaments, we can analyze the given options step by step.

### Step 1: Identify the acids listed in the options.
The options provided are:
- A) HCl (Hydrochloric acid)
- B) H2SO4 (Sulfuric acid)
- C) HNO3 (Nitric acid)
- D) H3PO4 (Phosphoric acid)

### Step 2: Understand the purpose of cleaning gold and silver.
Gold and silver ornaments can accumulate dirt, tarnish, or sulfide layers over time, which dulls their appearance. Goldsmiths need an effective method to clean these metals without damaging them.

### Step 3: Analyze the properties of each acid.
- **HCl (Hydrochloric acid)**: This acid can react with metals, potentially damaging the gold and silver.
- **H2SO4 (Sulfuric acid)**: This is also a strong acid that can react with metals and may not be suitable for cleaning delicate ornaments.
- **HNO3 (Nitric acid)**: This acid is known to be a strong oxidizing agent. Importantly, it does not react with gold or silver in a way that would damage them; instead, it can effectively remove tarnish and dirt.
- **H3PO4 (Phosphoric acid)**: This acid is generally milder and may not be effective for cleaning metals.

### Step 4: Determine the correct answer.
Given the properties of the acids, **HNO3 (Nitric acid)** is the most suitable choice for cleaning gold and silver ornaments because it effectively removes tarnish without reacting with the metals themselves.

### Final Answer:
The acid used by goldsmiths for cleaning gold and silver ornaments is **C) HNO3 (Nitric acid)**.

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