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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Ionic bonding is the complete transfer of valence electron(s) between atoms. It is a type of chemical bond that generates two oppositely charged ions. In ionic bonds, the metal loses electrons to become a positively charged cation, whereas the nonmetal accepts those electrons to become a negatively charged anion.
Explanation:
As a neutral lithium atom contains 3 protons and its elemental charge is given as
. Hence, we will calculate its number of moles as follows.
Moles = 
= 
= 100 mol
According to mole concept, there are
atoms present in 1 mole. So, in 100 mol we will calculate the number of atoms as follows.
No. of atoms = 
=
atoms
Since, it is given that charge on 1 atom is as follows.

= 
Therefore, charge present on
atoms will be calculated as follows.

Thus, we can conclude that a positive charge of
is in 0.7 kg of lithium.
Answer:
The correct answer is A. 140 atm
Explanation:
We use the gas formula, which results from the combination of the Boyle, Charles and Gay-Lussac laws. According to which at a constant mass, temperature, pressure and volume vary, keeping constant PV / T. We convert the unit Celsius into Kelvin:
0 ° C = 273K, 67 ° C = 273 + 67 = 340K; 94 ° C = 273 + 94 = 367K
P1xV1 /T1= P2x V2/T2
P2= ((P1xV1 /T1)xT2)/V2
P2=((88,89atm x 17L/340K)x367K)/12L= <em>135,927625 atm</em>