Final answer:
The left-hand thread is used for acetylene tanks for safety, ensuring correct connections in welding. In oxyacetylene torches, a mixture of acetylene and oxygen produces a high-heat flame, and the combustion reaction requires 2.5 volumes of oxygen for each volume of acetylene. To burn 9340 L of acetylene completely, approximately 4 tanks of oxygen are needed.
Step-by-step explanation:
The purpose of a left-hand thread is often for safety to prevent incorrect connections. Specifically, in the context of welding, a left-hand thread is used for acetylene tanks. This helps distinguish them from oxygen tanks, which typically use a right-hand thread. Acetylene is highly combustible and is used in oxyacetylene torches for cutting and welding metals due to the high heat of combustion it produces. When it comes to an acetylene torch, the correct mixture and flow of acetylene and oxygen are crucial to create an efficient and hot flame.
For the combustion of acetylene in a welding torch, the chemical reaction with oxygen is 2 C₂H₂ + 5 O₂ → 4 CO₂ + 2 H₂O. This means that for each volume of acetylene (C₂H₂), two and a half times that volume of oxygen (O₂) is required for complete combustion. So, to calculate how many tanks of oxygen are needed to burn 9340 liters of acetylene, we use the provided information. Each oxygen tank provides 7000 liters of oxygen, and we need 2.5 times the acetylene volume which is 9340 L * 2.5 = 23350 liters of oxygen. To find the number of oxygen tanks required, we divide 23350 liters by 7000 liters per tank, which results in approximately 3.34 tanks. Since you can't have a fraction of a tank, you would need at least 4 tanks of oxygen to fully combust the acetylene.