2.) Average atomic mass =Σ (abundance x molar mass) /100
= (12.64 x 302.04 + 18.23 x 304.12 + 69.13 x 305.03) /100
=304.486 u(Dalton) . This is avg atomic mass.
The independent variable would be the variable in the research that is being manipulated by the researcher. In this case, it would be temperature in the cage as it is what is being manipulated and changed in the research design. The dependent variable would be the variable that is being studied so, for this case, it would be the length and the weight of the mice. The constants are the factors that might affect the dependent variable but is held constant or the same by the researcher throughout the experiment. These are the size of the cage, amount of food and the exercise wheel. The flaw that the scientist would be studying the length of the mice since I don't think the temperature has any effect on it. And base from he results, the change in lengths are not conclusive.
Ca, V, Cu, Kr
Remember a period is a the horizontal rows in the Periodic Table.
Answer: E. It decreases the value of Eact.
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 is regenerated as such at the end.
Answer : The enthalpy change for dissolving this salt on a energy per mass basis is 132.4 J/g
Explanation :
Heat released by the reaction = Heat absorbed by the calorimeter + Heat absorbed by the water
![q=[q_1+q_2]](https://tex.z-dn.net/?f=q%3D%5Bq_1%2Bq_2%5D)
![q=[c_1\times \Delta T+m_2\times c_2\times \Delta T]](https://tex.z-dn.net/?f=q%3D%5Bc_1%5Ctimes%20%5CDelta%20T%2Bm_2%5Ctimes%20c_2%5Ctimes%20%5CDelta%20T%5D)
where,
q = heat released by the reaction
= heat absorbed by the calorimeter
= heat absorbed by the water
= specific heat of calorimeter = 
= specific heat of water = 
= mass of water = 
= change in temperature = 
Now put all the given values in the above formula, we get:
![q=[(42.2J/^oC\times 0.93^oC)+(75.0g\times 4.184J/g^oC\times 0.93^oC)]](https://tex.z-dn.net/?f=q%3D%5B%2842.2J%2F%5EoC%5Ctimes%200.93%5EoC%29%2B%2875.0g%5Ctimes%204.184J%2Fg%5EoC%5Ctimes%200.93%5EoC%29%5D)

Now we have to calculate the enthalpy change for dissolving this salt on a energy per mass basis.

where,
= enthalpy change = ?
q = heat released = 331.08 J
m = mass of salt = 2.50 g

Therefore, the enthalpy change for dissolving this salt on a energy per mass basis is 132.4 J/g