(5 points) how many moles of oxygen are necessary to completely react with propane
(c3h8) to produce 16.3 mol of water according to the following balanced chemical
equation?
c3h8 + 5 o2  3 co2 + 4 h2o
7. (10 points) what mass of barium hydroxide is necessary to react with 253 g of
phosphoric acid (h3po4) according to the following balanced chemical equation?

2 h3po4 + 3 ba(oh)2  ba3(po4)2 + 6 h2o
8. (5 points) what volume of carbon dioxide (co2) gets produced when 8.0 l of octane
(c8h18) react with excess oxygen according to the following balanced chemical
equation?
2 c8h18 + 25 o2  16 co2 + 18 h2o

you need to take a look at the periodic system in order to sort these elements into pairs that would most likely exhibit similar chemical properties. first, you need to find elements that are found in the same group (groups are vertical in the periodic system), and then to see whether they have the same valence number. if they meet these criteria, they will have similar properties.

the first pair: ne (neon) and kr (krypton), are noble gases found in group 8

the second pair: li (lithium) and k (potassium), found in group 1

the third pair: s (sulfur) and te (tellurium), found in group 6

the correct option is c.

isotopes refers to different forms of the same element with the same atomic number but different mass number as a result of difference in their neutron numbers. isotopes have different relative atomic mass but share the same chemical properties.