Answer : The correct option is, Only Student B
Explanation :
Lewis-dot structure : It shows the bonding between the atoms of a molecule and it also shows the unpaired electrons present in the molecule.
In the Lewis-dot structure the valance electrons are shown by 'dot'.
The given molecule is, 
As we know that nitrogen has '5' valence electrons and hydrogen has '1' valence electron.
Therefore, the total number of valence electrons in = 5 + 3(1) = 8
According to Lewis-dot structure, there are 6 number of bonding electrons and 2 number of non-bonding electrons.
The Lewis dot structure of student A is wrong because there is a coordinate bond present between the nitrogen and hydrogen is not covalent.
Thus, the correct Lewis-dot structure of is shown by the student B.
Answer:
Increasing the volume of the vessel
Explanation:
By the Le Chatelier's principle, if a system in equilibrium suffer a variation that disturbs the equilibriu, the reaction shift in the way to minimize the pertubation and re-establish the equilibrium.
For a variation in pressure, when it increases, the reaction shift for the smallest of gas volume, and if decreases, the reaction will shift for the large gas volume. So, for the reaction given, the products have the large amount of gas, so by decreasing the pressure, more products will be formed, and the amount of NH₄HS will reduce. To decrease the pressure, we can increase the volume of the vessel: for the ideal gas equation (PV= nRT), pressure and volume are indirectly proportional.
At 15.2°C. Kinetic energy of molecules highly depends on the temperature — the warmer it is, the faster the molecules will move, especially in fluids (gases and liquids). If we consider that the formula for average kinetic energy of molecules is:
Ek = 3/2*k*T where k is Boltzmanns constant and 3/2 is, well, 3/2, kinetic energy of molecules really only depends on the temperature.
Cu has two possible charges: plus 1 and plus 2. Thus, when copper is combined with an anion (negatively charged ion), the anion carries a subscript of one or two. This is shown in the given, Moreover, the given shows copper carries a subscript only of one. This means the anion has an original charge of negative one. These elements belong to the halogen family (Group 17).
Answer:- Mass of copper piece is 290 gram.
Solution:- We know that, mass = density * volume
density of copper is given as 8.96 gram per mL.
Volume of copper piece is the rise change in volume.
Volume of copper piece = 137 mL - 105 mL = 32 mL
Let's multiply the volume by density to calculate the mass of copper:
mass of copper = 
mass of copper = 286.72 g
Volume has two significant figures, so if we round the mass to two significant figures then it becomes 290 g.
