When some solid ammonium nitrate was dissolved in water the temperature decreased from 22 oC to 3 oC. What can be deduced from this observation? The dissolving is endothermic and ∆H is positive. The dissolving is endothermic and ∆H is negative. The dissolving is exothermic and ∆H is positive. The dissolving is exothermic and ∆H is negative.

Which is a correct statement about an endothermic reaction?
A. The bonds in the reactants are stronger than in the products and ∆H is positive.
B. The bonds in the products are stronger than in the reactants and ∆H is positive.
C. The bonds in the reactants are stronger than in the products and ∆H is negative
D. The bonds in the products are stronger than in the reactants and ∆H is negative.

Which is a correct statement about the following() enthalpy level diagram of a reaction? A. The reaction is exothermic and △H is positive.
E. The reaction is exothermic and △H is negative.
F. The reaction is endothermic and △H is positive.
G. The reaction is endothermic and △H is negative.

Which statements are correct for all exothermic reactions?
I. The products are more stable than the reactants.
II. The bonds in the products are stronger than the bonds in the reactants
III. The enthalpy of the products is less than the enthalpy of the reactants
A. I and II only
B. I and III only
C. II and III only
D. I, II and III

1. The dissolving is endothermic and deltaH is positive

2. A. The bonds in the reactants are stronger than in the products and deltaH is positive

3. I can't see the diagram so I don't know the answer (it's a glitch on my part not yours, my school district blocks images automatically on their rented chromebooks)

4.  A. I, and II only

Explanation:

   When we measure the temperature of a solution, and we notice that the temperature of the water is decreasing, then this is an endothermic reaction..

   The dissolved solute (the "invisible" ions) are absorbing the heat, causing the water around it to be colder.. **Heat moves from hot to cold, so the water is losing it's heat and the dissolving (dissolved solute) is gaining heat, meaning that it is Endothermic.

    When a reaction is endothermic, the energy that is required to break bonds and attractive forces is greater than the energy required to form bonds and attractive forces. This means that the bonds in the reactants are stronger than in the products and deltaH is positive. Since we know that the energy in the reactants is greater, there is more heat in the reactants. This is also why the dissolved solute would be gaining heat.. If the energy of the reactants is stronger, when it breaks, it will release a lot of energy that the dissolved solute will be absorbing.

     Think, heat (q, released or absorbed) is measured in Joules, the higher the Joules, the hotter something will be. So, if the heat (q) is negative, that represents the amount of Joules (heat) being released.  If it is positive, that is the amount being absorbed. So, if heat is being absorbed then deltaH is positive.  

    If the diagram shows the products being at a higher energy level than the reactants, then the diagram shows an endothermic reaction.. If we see that the energy from the products is greater, than the energy of the system increased as it absorbed energy from its surroundings.

If the diagrams shows the reactants being at a higher energy level than the products, then the diagram shows an exothermic reaction.. Think of it this way, if we see that the energy from the reactants was greater, than the energy of the system was originally greater than the surroundings, but now (observing the products), it is not, as energy was lost to the surroundings, making this an exothermic reaction.

    For exothermic reactions, the energy that is required to break bonds and attractive forces is less than the energy required to form bonds and attractive forces.. This means that energy in the products are greater, so as these bonds are broken and energy is released, the surroundings gain energy/heat. This means that the energy is favorable (more stable), the more negative our potential energy (energy of the system) is, the more favorable our process is.

the density of gold = 19.3 g/cm3

the relation between density and mass and volume is

density = mass / volume

given :

mass of gold = 13 g

density = 13g / volume = 19.3

volume = 13 /19.3 = 0.67 cm^3

thus volume of gold nugget = 0.67 cm^3