<span>Kind of substance besides water:
The best example of hydrogen bonding excluding water is DNA. The two strands of polymers are connected by hydrogen bonds between the nucleotide bases</span>.
Answer: Option (4) is the correct answer.
Explanation:
It is known that density is mass divided by volume.
Mathematically, Density = 
Since, density is directly proportional to mass. So, more is the mass of an element more will be its density.
Mass of magnesium is 24.305 g/mol.
Mass of barium is 137.327 g/mol.
Mass of beryllium is 9.012 g/mol
Mass of radium is 226 g/mol.
Hence, radium has more mass therefore it will have the greatest density at STP.
Formation reaction is the formation of 1 mole of product from the constituents of the reactant molecules. The mass of oxygen that must react is 182 gm.
<h3>What is mass and molar mass?</h3>
Mass of the substance is the weight while the molar mass of the substance is the addition of the atomic mass of the individual mass of the constituent atoms of the compound or the molecule.
The chemical reaction can be shown as:

From the reaction, it can be said that 3 moles of oxygen are required to produce 2 moles of aluminium oxide, so x moles of oxygen will be required to produce 3.80 moles of aluminium oxide.
Solving for x:

If 1 mol of oxygen is 32 gm then 5.7 moles of oxygen will be 182.4 gm.
Therefore, option D. 182 gm is the mass of oxygen required.
Learn more about moles and molar mass here:
brainly.com/question/893495
Answer: 0,4278g of F and 0,4191g of Fe
Explanation: it's possible to calculate the mass of each element by multiplying the percentage (decimal) of the element by the mass of the compound.
For Fluorine (F)
0,847g * 0,5051 = 0,4278g of F
For iron (Fe)
0,847 * 0,4949 = 0,4191g of Fe
This is determined because even when the compound is decomposed, due to conservative law of mass, the decomposition process do not affect the amount of matter, so the mass of the elements remain even if they are separated from the original molecule.
At the end, the sum of the elements masses should be the total mass of the compound.