Aclass is given a demonstration of solution chemistry and solubility equilibria. passage: a 6.57-g sample of niso4•6h2o (molar mass 262.84) is dissolved in enough water to make 50.00 ml of a green solution, and 7.15 g of na2co3•10h2o (molar mass 286.14) is dissolved in enough water to make 50.00 ml of a colorless solution. the two solutions are mixed, and a green precipitate forms. the resulting slurry is divided into two equal portions. to one portion is added an excess of 6 m hcl, which results in the disappearance of the precipitate and a rapid evolution of a gas. to the second portion is added a few milliliters of 6 m nh3. the precipitate dissolves, and a blue solution forms. question: according to the information in the passage, the gas that evolves is: a) sulfur dioxide. b) sulfur trioxide. c) carbon dioxide. d) carbon monoxide.

The gas that evolves must be carbon dioxide.

Explanation:

There is two reactions taking place: first, nickel sulfate reacts with sodium carbonate yielding sodium sulfate and nickel carbonate, which is a green solid. Then nickel carbonate reacts with hydrochloride, yielding nickel chloride, carbon dioxide and water.

1) NiSO4 (aq) + Na2SO4 (aq) = NiCO3 (s) + Na2SO4

2) NiCO3 (s) + 2 HCl (aq) = NiCl2 + CO2 + H2O

"among the transition metal elements, manganese and zinc have a slight lowering of electronegativities. the reason behind this is that the nuclear charges of these elements are slightly weaker than the other transition metal elements due to the way their valence electrons are filled up. both manganese and zinc have their valence electrons filled up to the 4th shell with 1 pair of electrons (4s2) completely occupying it. although the electrons in the 3rd shell (3d) are yet to be paired since the outer most shell is filled up, the ability of the nucleus to attract electrons is lessened. hence,   the electronegativity (or the ability to attract electrons) is lessened."

the potential energy of the reactants is 200j.

from the energy diagram, the energy of the product formed is 350j; this means that, this reaction is an endothermic reaction, because it absorbs energy from its environment.