A 26.9 g rock rolls down the Hill at a speed of 81.9 m/s. what is the kinetic energy of the rock?

90.21 J

Explanation:

Given that,

Mass of a rock, m = 26.9 g = 0.0269 kg

Speed of the rock, v = 81.9 m/s

We need to find the kinetic energy of the rock. It can be calculated using the formula as follows :

So, the kinetic energy of the rock is 90.21 J.

given:

mass of na = 115 g

excess cl2

to determine:

mass of nacl produced

explanation:

given reaction is-

2na(s) + cl2(g) → 2nacl(s)

since cl2 is in excess, na will be the limiting reagent

as per the reaction stoichiometry na: nacl = 1: 1

i.e. moles of na reacted = moles of nacl formed

now, # moles of na = mass of na/atomic mass

                                  = 115 g/23 g.mol-1 = 5 moles

therefore, moles of nacl = 5

molar mass of nacl = 58 g/mol

mass of nacl = 5 moles * 58 g.mol-1 = 290 g

ans: amount of nacl produced = 290 g