Your lab partner has carefully measured out 16.50 mL of water. You accidentally tip over the graduated cylinder and spill some of the water. You stand the cylinder up, and determine that there are 8.0 mL of water left. Which measurement is more precise-your lab partner’s or yours? Explain your answer.

Explanation:

In the measurement of 16.50 , the measuring scale is capable of measuring upto the depth of 1 / 100th of one mL . But In the measurement of 8.0 , the measuring scale is capable of measuring upto the depth of 1 / 10th of one mL

So the former is more precise because the second scale the measurement beyond 1/ 10 th is made by guesswork which may be faulty . So the former is more precise .

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