A hemoglobin molecule has a molecular weight of 67,200g/mol and contains 0.33% iron (Fe) by weight. Calculate the total number of iron atoms present in a single molecule of hemoglobin:

Determine the volume of CO₂ obtained by complete decomposition of 9.85 g of BaCO₃

1. 2.24 lit.

2. 1.12 lit.

3. 0.84 lit.

4. 0.56 lit

Find the minimum molecular weight of peroxidase anhydrous enzyme if the percentage of selenium (Se) in it is 0.5% by mass (atomic mass of Se = 78.4).

1. $1.568$ $\times$ ${10}^4$

2. $1.568$ $\times$ ${10}^3$

3. 15.68

4. $2.136$ $\times$ ${10}^4$

The mass of carbon anode consumed (giving only carbon dioxide) in the production of 270 kg of aluminum metal from bauxite by the Hall process is:

1. 90.0 kg

2. 540 kg

3. 180 kg

4. 270 kg

(Atomic mass: Al = 27)