Answer:
- The final result must be rounded to four significant figures and reported as 55.05 g NiCl₂.
Step-by-step explanation:
The molar mass of NiCl₂ is 129.5994 g/mol but you are using 129 g/mol, which is not quite accurate,
That means 129.5994 g NiCl₂ / 1 mol NiCl₂.
Thus, since you are starting with 0.4248 mol of NiCl₂ you can use the unit cancelation method to convert 0.4248 mol of NiCl₂ to grams.
The expression is:
- 0.4248 mol NiCl₂ × 129.5994g NiCl₂ / 1 mol NiCl₂
Notice that the unit mol NiCl₂ appears on the numerator of the first factor and on the denominator of the second factor, thus they cancel out, leaving only g NiCl₂ which is grams of NiCl₂.
The result of the operation is: 0.4248 × 129.5994 / 1 = 55.0538 and the units is gNiCl₂.
The other thing that you must take into account is the number of significant figure. You must consider that the 129.5994 gNiCl₂ is a constant; this is, an exact value that does not affect the number of significant figures.
Then, the result mus contain the same number of significant figures as the factor that is a measure. That is 0.4248 which has four significant figures.
Then, the final result must be rounded to four significant figures and reported as 55.05 gNiCl₂ instead of 55.0538 gNiCl₂.