Answer: Think and you will get it right!
Explanation:
To find the mass percent composition of an element, divide the mass contribution of the element by the total molecular mass. This number must then be multiplied by 100% to be expressed as a percent.
5. A
this is the answer check it out
Element atomic number position
Ba 56 group 2, period 6
Ca 12 group 2, period 3
S 16 group 16, period 3
Si `14 group 14, period 3
Now, you need to know the properties of the different type of elements and the tendencies on the periodic table.
The metallic elements are, those placed on the left side of the periodic table, are the ones that release an electron more easily, so they will requiere less energy to give it up when forming chemical bonds.
The higher the metallic character the less the energy need to give up an electron.
The metallic character grows as the group number decreases (goes to the left) period increases (goes downward), so among the elements considered, Barium will require the least amount of energy to give un an electron when forming chemical bonds.
<h3><u>Answer;</u></h3>
3.64 moles
<h3><u>Explanation;</u></h3>
From the equation;
2Cu + O2 → 2CuO
Mole ratio of Cu : CuO = 2: 2 equivalent to 1: 1
Moles of CuO = 3.64 Moles
Therefore;
moles of Cu will be ;
3.64 × 1 = 3.64 moles
Moles of Cu = <u>3.64 moles </u>
You must remember that oxidation number of hydrogen in acids is always +1, oxidation number of oxygen in oxides & acids is always -2... metals has always oxidation number on plus!
group NO3 comes from HNO3...and oxidation number of whole acid group is always on minus and equal to the amount of hydrogen atoms in this acid... so oxidation number of NO3 = -1
we have 2 NO3 groups so 2*(-1) = -2 and that is the reason why oxidation number of Fe in this formula must be +2... because sum of all elements always gives 0!
Now we could count of oxidation number for nitrogen... we write HNO3 and start counting from right to left:
3*(-2) from oxygens + 1 from hydrogen = -5
so nitrogen must have +5 oxidation number... because sum all in formula must be 0.
