Answer:
1) Endothermic.
2)
3)
Explanation:
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1) In this case, for these calorimetry problems, we can realize that since the temperature decreases the reaction is endothermic because it is absorbing heat from the solution, that is why the temperature goes from 22.00 °C to 16.0°C.
2) Now, for the total heat released by the reaction, we first need to assume that all of it is released by the solution since it is possible to assume that the calorimeter is perfectly isolated. In such a way, it is also valid to assume that the specific heat of the solution is 4.184 J/(g°C) as it is mostly water, therefore, the heat released by the reaction is:
3) Finally, since the enthalpy of reaction is calculated by dividing the heat released by the reaction over the moles of the solute, in this case NH4Cl, we proceed as follows:

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Best regards!
A. add a catalyst is the correct answer.
A catalyst never takes part in the reaction, so it does not affect the reaction.
Hope this helps~
Answer:
Solid ionic compounds do not conduct electricity because the ions are held firmly in place. The ions cannot move to conduct the electric current. But when an ionic compound melts, the charged ions are free to move. Therefore, molten ionic compounds do conduct electricity.
Answer:
Acceptable Lewis structure of Diatomic Nitrogen Molecule is as follow,
:N≡N:
Explanation:
The given lewis structure is acceptable because each nitrogen atom has a complete octet and and the formal charge of each nitrogen atom is zero. So those lewis structures which has zero or least formal charges are said to be more stable and acceptable. The formal charge is calculated is,
Formal Charge = # of Valence e⁻s - [# of non-bonded e⁻ + 1/2 # of bonded e⁻]
For N,
Formal Charge = 5 - [ 2 + 6/2]
Formal Charge = 5 - [ 2 + 3 ]
Formal Charge = 5 - 5
Formal Charge = 0
Same result will come for the second N atom.