Answer: Elements in Group 2
Explanation: The periodic table was arranged by Dmitri Mendeleev specifically around similarites in their chemical behaviors. He found that as atomic number increases, at some point an element starts to react in a manner similar to a previous one. When that happened, he would place the larger element under the smaller one, and eventually noticed a periodicity in the table. Elements in a column (Groups) had similiar chemical properties. We know today that these similarities are due to the electron configuration, and that these configurations repeat themselves. He left gaps in the table when he could find an existing element with properties similar to others in that group. I big leap of faith, but it worked. Elements for those missing boxes were eventually discovered.
Particles as small as atoms exist.
Answer:
157.8 g
Explanation:
Step 1: Write the balanced equation
Fe₂O₃ + 3 CO ⟶ 3 CO₂ + 2 Fe
Step 2: Calculate the moles corresponding to 209.7 g of Fe
The molar mass of Fe is 55.85 g/mol
209.7 g × 1 mol/55.85 g = 3.755 mol
Step 3: Calculate the moles of CO needed to produce 3.755 moles of Fe
The molar ratio of CO to Fe is 3:2. The moles of CO needed are 3/2 × 3.755 = 5.633 mol
Step 4: Calculate the mass corresponding to 5.633 moles of CO
The molar mass of CO is 28.01 g/mol.
5.633 mol × 28.01 g/mol = 157.8 g
