A reaction occurs when solid X is placed into solution Y. As a result, the temperature of the new solution increases by 3°C.
The temperature rises another 2°C when more of solid X is added to the solution. What does this indicate about the effect of
adding more solid?
O It increased the number of molecular collisions
O It decreased the number of molecular collisions
It decreased the space between the molecules and lowered the reaction rate.
It increased the space between the molecules and increased the reaction rate.

It increased the number of molecular collisions

Explanation:

When more amount of solid X is added to the solution, there is a increase in temperature of 2°C.

If the temperature of a solution increases by the addition of the salt, there must be increase in the movement of molecules.

These molecules move rapidly in the container, collide with each other and also these molecules collide with the walls of the container.

So as the temperature increases, number of molecular collisions also increases.  

a. energy is absorbed in the reaction.

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.

hey there!

mass = 6.75 g

volume =   9 cm³

therefore:

d = mass / volume

d   = 6.75 / 9

d = 0.7 g/cm³

answer b