Ca=40
C=12
O=16
1 mole of CaCO3 has 100 grams
So 50 grams is 0.5 mole
Answer:

Explanation:
Hello,
In this case, the combustion of methane is shown below:

And has a heat of combustion of −890.8 kJ/mol, for which the burnt moles are:

Whereas is consider the total released heat to the surroundings (negative as it is exiting heat) and the aforementioned heat of combustion. Then, by using the ideal gas equation, we are able to compute the volume at 25 °C (298K) and 745 torr (0.98 atm) that must be measured:

Best regards.
Answer : The oxygen will appears in the final chemical equation as a reactant.
Explanation :
The given chemical reactions are:
(1) 
(2) 
Now we are adding reaction 1 and reaction 2, we get the final chemical equation.
The final chemical equation is:

Thus, the oxygen will appears in the final chemical equation as a reactant.
Answer:
it stands for Hazardous Household Products Symbols.