Physical changes are changes affecting the form of a chemical substance, but not its chemical composition. Physical changes are used to separate mixtures into their component compounds, but can not usually be used to separate compounds into chemical elements or simpler compounds.
Ex: cutting a paper, gaining weight, cutting hair
Answer:
C. 100.7 amu
Explanation:
Isotopes of an element are atoms of an element with the same atomic number but different atomic masses. Each atomic mass of an isotope is known as an isotopic mass. An element that exhibits isotope, that is, that have two or more isotopes has a relative atomic mass that is not a whole number.
Relative atomic mass of X is the sum of the products of the relative abundances of each isotope and its isotopic mass.
For Isotope ¹⁰⁰X: 30% × 100 = 30 amu
For Isotope ¹⁰¹X: 70% × 101 = 70.7 amu
Relative atomic mass of X = (30 + 70.7) amu = 100.7 amu
Therefore, the approximate atomic mass of X is 100.7 amu
<u>Answer:</u>
A reaction is said to occur if there is a formation of an insoluble solid or a precipitate(s) or a liquid (l) or a gas(g).
If both the reactants and products are in aqueous state, No reaction takes place.
All chlorides and Bromides are soluble except that of Ag, Hg and Pb.
Hence, No reaction takes place since all the reactants and products are in aqueous states.
Salts of Group IA are soluble. Hence No reaction takes place
(REACTION TAKES PLACE)
All hydroxides are insoluble except that of Group IA, ammonium ion and Group IIA down from Calcium.
Hence Reaction takes place with the formation of 
precipitate
Answer: II. The catalyst provides a new pathway in the reaction mechanism.
III. The catalyst speeds up the reaction.
Explanation:
Activation energy is the extra energy that must be supplied to reactants in order to cross the energy barrier and thus convert to products.
A catalyst is a substance which increases the rate of a reaction by taking the reaction through a different path which involves lower activation energy and thus more molecules can cross the energy barrier and more molecules convert to products.
The catalyst itself does not take part in the chemical reaction and gets regenerated as such at the end of the reaction without getting consumed.
