We know that it is a certainty based on things such as the size, mass, brightness, etc. They can determine to within a relative level of accuracy the age. Of course they can be off by millions of years, but that’s pretty precise for a 10–20 billion year time period for the life of a star. BUT we absolutely cannot predict exactly when it will explode and we see supernovas in other galaxies, but the last one in the Milky Way that we observed was in the 1600s.
Explanation:
Sulfuric Acid (H2SO4) is a strong mineral acid that has is colorless when pure. This chemical is used as a chemical intermediate to manufacture other chemicals and cleaning metal surfaces. The formula for sulfuric acid is H2SO4. The molar mass of sulfuric acid is 98.07848 g mol.
Answer:
The octet rule refers to the tendency of atoms to prefer to have eight electrons in the valence shell. When atoms have fewer than eight electrons, they tend to react and form more stable compounds. When discussing the octet rule, we do not consider d or f electrons.
Explanation:
Answer is: because pH value of solution is changing.
Balanced chemical reaction: NaOH(aq) + HCl(aq) → NaCl(aq) + H₂O(l).
pH of sodium hydroxide solution is above seven (basic), when solution of hydrochloric acid is added, pH slowly dropping until it became neutral solution (pH is equal seven) and that is endpoint of titration.