Xg of U and 3.795 g of O combine to form 20.00 g of U308 . What is the percent composition of uranium in U308 ?
a
15.18%
b 42.41%
C 81.03%
d None of the above

The percent composition of Uranium in U308 = C. 81.03%

Given

X g of U

3.795 g of O

20.00 g of  U308

Required

The percent composition of Uranium

Solution

mass of Uranium in U308 :

= mass of U308 - mass of O

= 20 g - 3.795 g

= 16.205 g

The percent composition :

%U = (mass U/mass U308) x 100%

%U= (16.205/20) x 100%

%U = 81.025≈81.03

- "the choice that is not an indicator of a chemical change is "state of matter changes". more common than not, chemical reactions produce energy in the form of light or heat. along with energy, they also produce a new substance called the product that could be in any state of matter (solid, gas, or liquid)."

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