Hello, Jiwon. We often romanize 'ㄹ' as 'L' or 'R' for convenience, but actually there is no 'ㄹ' sound in English. When you pronounce 'L' you may put the tip of your tongue against the ridge above your top front teeth. But to pronounce 'ㄹ' I put my tongue to the palate RIGHT BEHIND THE FRONT TEETH. So when you say 몰라, you could try to put your tongue to the palate pronouncing '모'(mo). Then you could see it sounds like 'mol' but a little bit different. It's the same when 'ㄹ' comes to beginning of a word. For '라', while your tongue is at the palate, pronounce 'ㅏ' taking it off.

It's 몰라 [mol-la]. When ㄹ is in the end of a syllable, it sounds like "L". curry - 카레 - [ka-re] foot - 발 - [bal] water - 물 - [mul] Water is clean. - 물이 깨끗해. [mu-ri] in the water - 물 속에 [mul so-ge], 물 안에 [mu-ra-ne] Did you notice the difference? When ㄹ is followed by a vowel(이, 아, 오, 유, etc. : these are just one vowel without ㅇsound), it sounds like R-ish ㄹ. :-) You know what, there's even a pun about this '몰라'. Q : 너 '어금니'를 영어로 뭐라고 하는지 알아? (Do you know how they say '어금니' in English?) A : 몰라. (I don't know.) Q : 맞았어! 어떻게 알았지? ㅋㅋㅋ (That's correct! How did you know that? lol) The pronunciation of 'molar' is different from 몰라[mol-la]. But they sound similar to Koreans. (In some province, they sound a lot similar. -0-) ㅋㅋ Did you get this joke? :-)