In normal oxy acetylene welding, which gases are commonly used to produce the high temperature flame needed for welding metals?

Introduction / Context:
Welding is a common industrial process that joins metals using heat. One traditional and widely taught method is gas welding, specifically oxy acetylene welding. In this technique, the flame is produced by burning a fuel gas in oxygen, achieving temperatures high enough to melt steel. Understanding which gases are used in standard welding equipment is an important part of applied chemistry and engineering awareness.

Given Data / Assumptions:

• The question refers to normal welding using a gas flame, typically meaning oxy acetylene welding.
• Common fuel gases include acetylene, hydrogen, and others, but not all are standard for normal welding.
• The options list combinations of oxygen, acetylene, nitrogen, and hydrogen.
• We assume basic industrial practice where the most common setup is required.

Concept / Approach:
In oxy acetylene welding, acetylene (C2H2) is used as the fuel gas because it produces a very hot flame when burned in oxygen, reaching temperatures around 3000 degrees Celsius or more. Oxygen is supplied from a high pressure cylinder to support complete combustion of acetylene. Nitrogen is relatively inert and would not support such a hot flame, and while hydrogen can be used for some specialised welding or cutting processes, the classic and most widely taught gas welding combination is oxygen with acetylene.

Step-by-Step Solution:
Step 1: Identify the standard welding method implied. The phrase normal welding by gas usually refers to oxy acetylene welding. Step 2: Recall the gases used in oxy acetylene welding. Acetylene is the fuel gas, and oxygen is the supporter of combustion. Step 3: Compare with the options. Option A lists oxygen and acetylene, exactly matching the standard pair. Other options include nitrogen or hydrogen combinations that are not typical for standard oxy acetylene welding.

Verification / Alternative check:
Practical welding manuals and vocational training material describe the gas welding torch as having two supplies: one from an oxygen cylinder and the other from an acetylene cylinder. The flame produced is specifically called an oxy acetylene flame. While other fuel gases such as liquefied petroleum gas or hydrogen may be used for specialised tasks, they are less common in basic metal welding instruction. This confirms that the correct answer must include only oxygen and acetylene.

Why Other Options Are Wrong:
Option B: Acetylene and nitrogen would not give a strong welding flame because nitrogen does not support combustion in the same way oxygen does. Option C: Oxygen, hydrogen, and acetylene together is not a standard combination and would complicate flame control, so it is not used as the normal welding setup. Option D: Oxygen and hydrogen can produce a flame, but this oxy hydrogen flame is less common for general metal welding and is not usually referred to as normal welding gas in basic chemistry questions.

Common Pitfalls:
Students may be tempted to select any option that includes oxygen, forgetting that a specific fuel gas must also be chosen. Another mistake is thinking nitrogen participates in combustion because it is a major component of air, but in reality nitrogen is largely inert. Remember the familiar phrase oxy acetylene welding to fix in mind that the classic combination is oxygen plus acetylene.

Final Answer:
The gases used in normal oxy acetylene welding are Oxygen and Acetylene.