D
Avogadro's number allows us to measure the amount of atoms or molecules in one mole of a substance.
Answer:
1. Hot water
2. A pile of wood shavings
Explanation:
Sugar can dissolve more quickly in hot water than in cold water because there is more energy in hot water molecules. Because they are moving faster, they have more energy to break the bonds that hold sugar together. There is also more energy available to break the hydrogen bonds that hold water together.
Wood shavings have a greater contact surface than the solid hunk of wood, which is why they have a higher calorific value and then they will catch fire more easily.
Answer:
The mass percentage of calcium carbonated reacted is 2.5%.
Explanation:
The reaction is:

Thus the Kp of the equilibrium will be:
Kp = partial pressure of carbon dioxide [as the other are solid]
Moles of calcium carbonate initially present = 
Let us apply ICE table to the equilibrium given:

Initial 0.2 0 0
Change -x +x +x
Equilibrium 0.2-x x x
Kp = partial pressure of carbon dioxide
Kp = Kc(RT)ⁿ
where n = difference in the number of moles of gaseous products and reactants
for given reaction n = 1
R = gas constant = 8.314 J /mol K
T = temperature = 800 ⁰C = 1073 K
Putting values
Kc =
Kc = ![\frac{[CO_{2}][CaO]}{[CaCO_{3}]}= \frac{x^{2} }{(0.2-x)}=1.3X10^{-4}](https://tex.z-dn.net/?f=%5Cfrac%7B%5BCO_%7B2%7D%5D%5BCaO%5D%7D%7B%5BCaCO_%7B3%7D%5D%7D%3D%20%5Cfrac%7Bx%5E%7B2%7D%20%7D%7B%280.2-x%29%7D%3D1.3X10%5E%7B-4%7D)


On calculating
x = 0.005
where x = the moles of calcium carbonate dissociated or reacted.
Percentage of the moles or mass reacted =
%