Gas x would be carbon dioxide.
note/ acid + carbonate —> salt + water + carbon dioxide
the white precipitate would be calcium carbonate. CaCo₃
note/ this is a common eqn u need to remember.
X - CO₂ (carbón dioxide)
Y - CaCo₃ (calcium carbonate)
sodium carbonate is a basic salt
They all look like there decaying and was left out or sat inside too long
Explanation:
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Sedimentary rocks don't necessarily make fossils. Although when animals die on top of the rocks and are never moved, blown away, etc they can get trapped under the growing rock. Which is why fossils are often found in sedimentary rocks.
I haven't got the answer but I'm probably sure that u can actually look up that answer hoped it help
