Would you please help need asap The analysis of a compound gives the following percent composition by mass:
C: 56.70 percent; H: 8.419 percent; S: 11.65 percent; O: 23.24 percent. What is its molecular formula, given that its molar mass is 275.4 g?

C?H?S?O?
C atoms
H atoms
S atoms
O atoms

What protects the lining of the stomach from acidic gastric juices?

Can someone i have no idea of how to do this.

Based on the observation that only male crickets produce a song, you hypothesize that a male's song is a form of communication to potential mates. you set up a simple experiment to test this hypothesis. in the laboratory, you place a male snowy tree cricket in enclosure a, which is adjacent to enclosureb. in enclosure b, you place other insects, one at a time, and observe their responses to the male's song. the enclosures are designed so that the two insects being tested cannot see or smell each other, but sound is transmitted from enclosure a to enclosureb.