Question

The total number of calcium atoms in the expression 3 cos 2 shown in the equation 3 CaCl 2 +2Na 3 PO 4 Ca(PO 4 ) 2 +6 NaCl is:

Answer 1

`C`

Step-by-step explanation:

Here, we want to calculate the percentage composition of the compound formed when oxygen reacts with iron

We have the equation of reaction as follows:

`4Fe_((s))\text{ + }3O_(2(g))\text{ }\rightarrow\text{ }2Fe_2O_(3(s))`

The compound formed is Fe2O3

Now, let us get its percentage composition

The molar mass of the compound is 160 g/mol

The atomic mass of iron is 56 amu

The atomic mass of oxygen is 16 amu

Now, let us get the percentage composition:

`\begin{gathered} \text{Iron = }(2*56)/(160)\text{ }*\text{ 100 \% = }70\text{ \%} \\ \\ \text{Oxygen = }(3*16)/(160)\text{ = 30\% } \end{gathered}`

The closest here is thus the option C