How many atoms are in 149 grams of calcium?

How many molecules of sucrose c12h22o11 are there in 454 grams of sucrose

In numbering carbon atoms in the parent chain of a hydrocarbon, why would you number from right to left, rather than left to right

Kc = 0.040 for the system below at 450oc. if a reaction is initiated with 0.40 mole of cl2 and 0.40 mole of pcl3 in a 2.0 liter container, what is the equilibrium concentration of cl2 in the same system? pcl5(g) ⇄ pcl3(g) + cl2(g)