Determine the number of significant in 400

400 or 4x102 indicates only onesignificant figure. (To indicate that the trailing zeros are significant a decimal point must be added. 400. has threesignificant digits and is written as 4.00x102 in scientific notation.) Exact numbers have an infinite number of significant digits but they are generally not reported.

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

i think its 100

i hope this !