Answer: (3)
Medeleev arranged elements in order of increasing atomic weight and similar properties
He noticed that similar elements were grouped together by using this.
Answer:
1 has the highest density because it has the most amount of circles in the least amount of space- it is the most densely filled with circles; it is the most dense.
The net amount of energy produced can be obtained from a table of enthalpy change of formation, available online.
The enthalpy change of formation indicate how much energy the 1 mole of the product (H2O) has relative to the elemental reactants (H2 and O2). In other words, the "lost" energy equals the heat/energy released.
For water (H2O), this value is -285.8 if the final product is a liquid under standard conditions, and -241.82 if the product is in gas form which contains some energy that could be further released. This means that if the final product (H2O) is in liquid form, energy released is 285.8 kJ/mol.
Since water is in liquid form under standard conditions, the first value (285.8 kJ/mol) is generally appropriate.
Oxygen,hydrogen, and carbon
