Nitrous Acid.
Hyponitrous acid: H2N2O2
Nitric acid: HNO3
Pernitric acid: HNO
The experimental density of CO2 at STP is 0.10/0.056=1.78 g/L. The percent error equals to (1.96-1.78)/1.96*100%=9.18%. So the answer is 9.18%.
Fe2O3 because O has a -2 charge and Fe and +3, you want the charges to equal each other so if you have 2 Fe with +3 charge the charge becomes 6 if you have 3 O with -2 charge the charge becomes 6.
The answer is (2) 10.0 mol. The equation given is balanced. So the ratio of mol number of compound is the ratio of the number before the compound. The HCl and CO2 ratio is 2:1. So the answer is 10.0 mol.
Sodium represents by the (Na).
