The answer is motion, this is what I would go with because when you are dealing with gases it puts motion in the term of particles.
Answer : The mass in grams of calcium sulfate is 0.16 grams.
Explanation :
Molarity : It is defined as the number of moles of solute present in one litre of solution.
Formula used :
Solute is, 
Given:
Molarity of = 0.0025 mol/L
Molar mass of = 136 g/mole
Volume of solution = 485 mL
Now put all the given values in the above formula, we get:
Thus, the mass in grams of calcium sulfate is 0.16 grams.
Explanation:
Reaction equation for the given chemical reaction is as follows.
Equation for reaction quotient is as follows.
Q = 
= 
= 0.256
As, Q > K (= 0.12)
The effect on the partial pressure of 
as equilibrium is achieved by using Q, is as follows.
- This means that there are too much products.
- Equilibrium will shift to the left towards reactants.
- More is formed.
- Partial pressure of increases.
Answer is: a. Rubidium (Rb) is more reactive than strontium (Sr) because strontium atoms must lose more electrons.
The ionization energy (Ei) is the minimum amount of energy required to remove the valence electron, when element lose electrons, oxidation number of element grows (oxidation process).
Alkaline metals (group 1), in this example rubidium, have lowest ionizations energy and easy remove valence electrons (one electron), they are most reactive metals.
Earth alkaline metals (group 2), in this example strontium, have higher ionization energy than alkaline metals, because they have two valence electrons, they are less reactive.
Rubidium electron configuration: ₃₇Rb 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶5s¹; one valence electron is 5s¹ orbital.
Strontium electron configuration: ₃₈Sr 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶5s²; two valence electrons is 5s² orbital.
