Answer: 
Explanation:
A double displacement reaction is one in which exchange of ions take place. The salts which are soluble in water are designated by symbol (aq) and those which are insoluble in water and remain in solid form are represented by (s) after their chemical formulas.
The balanced chemical equation when when aqueous solutions of chromium(III) sulfate and calcium nitrate are combined is:

Oxygen gas expands in a container and when pressure is applied it liquifies and occupies a smaller volume
hope that helps <span />
Answer:
it is B because the other answers logically dont fit in
Answer:
O a 2 in front of hydrochloric acid
Explanation:
the given reaction is :-
=》Zn + 2 HCL -> ZnCl2 + H2
since, mass can't be created or destroy, so number of hydrogen atoms in the reaction should be equal in product as in reaction.
so, there is 2 hydrogen in product hence there are two hydrogen in the reactants also.
it is showed in the reaction by putting a 2 in front of hydrochloric acid ( HCl ).
<span>

is directly related to the ideal gas law.
The ideal gas law states that:

. Rewriting this gives:

. R is the universal gas constant, so its value is fixed. For a given sample, n is the number of moles of the gas, so its value would be fixed too. This means that the value of

would be a fixed constant as well. Therefore, whatever the initial value

is, it should be equal to the final value

.</span>