Assertion (A): The main component of natural gas is butane. Reason (R): Butane is easily liquified under pressure

Assertion (A) is false because the main component of natural gas is methane (CH4), not butane. Methane typically constitutes 80 to 90 percent of natural gas [3][t3]. While butane is present in natural gas, it is considered a minor constituent or a 'natural gas liquid' (NGL) [1][t6][t7]. Reason (R) is true because butane has a critical temperature (425 K or 152 °C) well above room temperature, allowing it to be easily liquefied under pressure at ambient temperatures [t4][t8]. In contrast, methane has a very low critical temperature (-82.6 °C), making it much harder to liquefy, requiring cryogenic temperatures for storage as Liquefied Natural Gas (LNG) [t4][t5]. Therefore, while butane's ease of liquefaction is a known physical property, the assertion regarding its dominance in natural gas is incorrect.

Sources

1. [1] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 9: Distribution of World Natural Resources > natural gas as a Resource > p. 15
2. [3] https://nvlpubs.nist.gov/nistpubs/Legacy/IR/nbsir85-3028.pdf