A. The number of valence electrons increases as atomic mass increases. == Generally true for the representative elements since atomic mass generally increases with increasing Z.
B. The reactivity of alkali metals increases as atomic mass increases. == True. Atomic mass increases down the column and so does reactivity
C. The reactivity of the halogens increases as atomic mass increases. == False. Reactivity decreases down the column.
D. The number of valence electrons decreases across a period. == False. In general, the number of valence electrons increases across a period, particularly for the representative elements.
Another compound that can be used to treat acidic soil is calcium carbonate.<span />
To do this, you would first add together the molar mass of all involved elements, to find how many grams are in a mole of Cu(OH)2. Keep in mind, the molar mass is equal to the atomic mass of an element in grams. For example the molar mass of copper (Cu) would be 63.55 (with 2 sig. figs.)
Therefore, now we add together the mass of all elements involved.
Cu: (63.55)+O2(15.99x2=31.98)+H2(1.01x2=2.02)
63.55+31.98+2.02= 97.55g per mole of Cu(OH)2.
Now, divide what we have by how much it takes to get a mole of the stuff.
68.1/97.55= 0.698mol Cu(OH)2
The correct answer would be B for sure
