Question

calculate how many atoms of each element are present in the following compounds. the first one has been done as an example.
4caco₃
calcium carbonate - heartburn treatment
3h₂o₂
hydrogen peroxide
4fes₂

Explanation:

Step1: Analyze $4CaCO_3$

For $CaCO_3$, the coefficient is 4. There is 1 Ca atom in one $CaCO_3$ unit. So number of Ca atoms = $4\times1 = 4$. There is 1 C atom in one $CaCO_3$ unit, so number of C atoms = $4\times1=4$. There are 3 O atoms in one $CaCO_3$ unit, so number of O atoms = $4\times3 = 12$.

Step2: Analyze $3H_2O_2$

For $H_2O_2$, the coefficient is 3. There are 2 H atoms in one $H_2O_2$ unit. So number of H atoms = $3\times2=6$. There are 2 O atoms in one $H_2O_2$ unit, so number of O atoms = $3\times2 = 6$.

Step3: Analyze $4FeS_2$

For $FeS_2$, the coefficient is 4. There is 1 Fe atom in one $FeS_2$ unit. So number of Fe atoms = $4\times1 = 4$. There are 2 S atoms in one $FeS_2$ unit, so number of S atoms = $4\times2=8$.

Answer:

Compound	Element	Number of Atoms
$4CaCO_3$	C	4
$4CaCO_3$	O	12
$3H_2O_2$	H	6
$3H_2O_2$	O	6
$4FeS_2$	Fe	4
$4FeS_2$	S	8