Question

section 1
explaining marble changes in the taj mahal by openscied
the taj mahal was built in agra, india by the emperor shah jahan as a memorial for his wife. it
was completed around 1653. it is an impressive building created out of white marble.
however, in the last 50 years, people have noticed that the building is turning from white to
yellow and the marble is cracking and falling apart.

the marble used to build the taj mahal is made mostly of one substance: calcium carbonate.
scientists suspect that chemical reactions between a substance that is coming into contact
with the calcium carbonate in the marble might be causing it to break down.

3 the chemical formula for calcium carbonate is caco₃. what are the
elements in calcium carbonate (caco₃)?
(a)
a calcium, carbon, oxygen
b calcium, arsenic, carbon, oxygen
c carbon, oxygen
d calcium, carbon
(b) how many atoms of oxygen are in a calcium carbonate (caco₃ ) molecule?
a 4
b 1
c 3
d 2

Explanation:

For part (a), in the chemical formula \(CaCO_3\), \(Ca\) represents calcium, \(C\) represents carbon, and \(O\) represents oxygen. There is no arsenic (\(As\)) in the formula, so option B is wrong. Options C and D miss some elements.
For part (b), in the formula \(CaCO_3\), the subscript of \(O\) is 3, which means there are 3 oxygen atoms in one calcium carbonate molecule.

Answer:

(a) A. calcium, carbon, oxygen
(b) C. 3