Sorry I cant I just need some points
Answer:
C) Potassium, K, and calcium, Ca
Explanation:
Given pair of elements:
Ni and Cu
Potassium and Ca
Nitrogen and oxygen
Solution:
We know that number of protons and number of electrons are always equal and number of electron or number of proton is called atomic number.
Number of protons given elements:
Ni number of protons = 28
Copper number of protons = 29
Combine number of protons = 57
K number of protons = 19
Ca number of protons = 20
Combine number of protons = 39
Ni number of protons = 7
O number of protons = 8
Combine number of protons = 15
Thus, option C is correct.
Answer:
23.6 moles
Explanation:
From the question given above, the following data were obtained:
Mass of air = 3.6 Kg
Mass percentage of O₂ = 21%
Number of mole of O₂ =?
Next, we shall convert 3.6 Kg of air to grams (g). This can be obtained as follow:
1 kg = 1000 g
Therefore,
3.6 Kg = 3.6 Kg × 1000 / 1 kg
3.6 Kg = 3600 g
Next, we shall determine the mass of O₂ in the air. This can be obtained as follow:
Mass of air = 3600 g
Mass percentage of O₂ = 21%
Mass of O₂ =?
Mass of O₂ = 21% × 3600
Mass of O₂ = 21/100 × 3600
Mass of O₂ = 756 g
Finally, we shall determine the number of mole of O₂ in the sample of air. This can be obtained as follow:
Mass of O₂ = 756 g
Molar mass of O₂ = 2 × 16 = 32 g/mol
Number of mole of O₂ =?
Mole = mass /Molar mass
Number of mole of O₂ = 756 / 32
Number of mole of O₂ = 23.6 moles
Thus, the number of mole of O₂ in the
sample of air is 23.6 moles
