Question 5)
1 Hour: 100g
40 Minutes: 50g
20 Minutes: 25g
0 Minutes: 12.5g
Question 6)
160 Days: 80ou
120 Days: 40ou
80 Days: 20ou
40 Days: 10ou
0 Days: 5ou
Every period of time, the radioactive isotopes halve in numbers as they emit radiation.
I think you now know the gist. Try doing the rest yourself.
Good luck.
Answer:
Option D.
Explanation:
First we convert the given reactant masses into moles, using their respective molar masses:
- 4.00 g H₂ ÷ 2 g/mol = 2 mol H₂
- 6.20 g P₄ ÷ 124 g/mol = 0.05 mol P₄
0.05 moles of P₄ would react completely with (6*0.05) 0.3 moles of H₂. There are more H₂ moles than required, meaning H₂ is in excess and P₄ is the limiting reactant.
Now we<u> calculate how many PH₃ moles could be formed</u>, using the <em>number of moles of the limiting reactant</em>:
- 0.05 mol P₄ *
= 0.2 mol PH₃
Finally we <u>convert 0.2 mol PH₃ into grams</u>, using its <em>molar mass</em>:
- 0.2 mol PH₃ * 34 g/mol = 6.8 g
So the correct answer is option D.
In a solid state, the molecules have the least amount of energy. They just stick close together and vibrate in place. As the molecules gain more energy, they are able to move around more freely. In the liquid state, the molecules have enough energy to sort of tumble over each other.
First we calculate the concentration of HCl:
Moles = mass / Mr
= 25 / 36.5
= 0.685 mol
Concentration = 0.685/1.5 = 0.457 mol / dm³
For a strong monoprotic acid, the concentration of hydrogen ions is equal to the acid concentration.
pH = -log[H+]
pH = -log(0.457)
= 0.34
The right answer is D - mass.