A formula unit is the same as the empirical formula of a compound or an ionic molecule. It is the lowest ratio of the atoms in the compound or ion. Zinc acetate ions dissociates into zinc ions and acetate ions. The dissociation reaction is expressed as follows:
Zn(O2CCH3)2 = Zn2+ + 2(O2CCH3)1-
We determine the amount of acetate ions produced as follows:
Moles Zn(O2CCH3)2 = (3 formula units Zn(O2CCH3)2) ( 1 mol / 6.022x10^23 formula units) = 4.98x10^-24 mol Zn(O2CCH3)2
moles (O2CCH3)1- = 4.98x10^-24 mol Zn(O2CCH3)2 ( 2 mol (O2CCH3)1- / 1 mol Zn(O2CCH3)2 ) = 9.96x10^-24 mol (O2CCH3)1-
# of acetate ions = 9.96x10^-24 mol (O2CCH3)1- ( 6.022x10^23 ions / 1 mol (O2CCH3)1-) = 6 acetate ions
Answer:
The amount left after 49.2 years is 3mg.
Explanation:
Given data:
Half life of tritium = 12.3 years
Total mass pf tritium = 48.0 mg
Mass remain after 49.2 years = ?
Solution:
First of all we will calculate the number of half lives.
Number of half lives = T elapsed/ half life
Number of half lives = 49.2 years /12.3 years
Number of half lives = 4
Now we will calculate the amount left after 49.2 years.
At time zero 48.0 mg
At first half life = 48.0mg/2 = 24 mg
At second half life = 24mg/2 = 12 mg
At 3rd half life = 12 mg/2 = 6 mg
At 4th half life = 6mg/2 = 3mg
The amount left after 49.2 years is 3mg.
False
Although we use many of their ideas to describe atoms today, such as the existence of a tiny, dense nucleus in an atom (proposed by Rutherford), or the notion that all atoms of an element are identical (proposed by Dalton), some of their ideas have been rejected by the modern theory of the atom.
For example, Thompson came up with the plum pudding model to describe an atom, which resembled a sphere of positive charge with electrons embedded in it. We know now, however, that atoms are mostly empty space with a tiny, dense nucleus.
Another example is Dalton's atomic theory, which stated that atoms are indivisible particles. However, this was disproved by the discovery of subatomic particles.
The balanced equation for the above reaction is as follows;
2C₁₀H₂₂ + 31O₂ ---> 20CO₂ + 22H₂O
stoichiometry of C₁₀H₂₂ to CO₂ is 2:20
this means that for every 2 mol of C₁₀H₂₂ that reacts - 20 mol of CO₂ is formed
therefore when 5.0 mol of C₁₀H₂₂ reacts - 20/2 x 5.0 = 50 mol of CO₂ is formed
50 mol of CO₂ is produced.
Step 1 : Write balanced chemical equation.
CaF₂ can be converted to F₂ in 2 steps. The reactions are mentioned below.
I] 
II] 
The final balanced equation for this reaction can be written as
Step 2: Find moles of CaF₂ Using balanced equation
We have 1.12 mol F₂
The mole ratio of CaF₂ and F₂ is 1:1
Step 3 : Calculate molar mass of CaF2.
Molar mass of CaF₂ can be calculated by adding atomic masses of Ca and F
Molar mass of CaF₂ = Ca + 2 (F)
Molar mass of CaF₂ = 40.08 + 18.998 = 78.08 g
Step 4 : Find grams of CaF₂
Grams of CaF₂ = 
Grams of CaF₂ = 87.45 g
87.45 grams of CaF2 would be needed to produce 1.12 moles of F2.
