University Of Central Florida (UCF) CHM2045C Chemistry Fundamentals I Practice Exam 1

To find the total mass when adding 15 g of H2O and 1.350 g of NaCl, you begin by summing these two values: \[ 15 \, \text{g (H2O)} + 1.350 \, \text{g (NaCl)} = 16.350 \, \text{g} \] When rounding this total to the correct number of significant figures, it is important to recognize that the mass of water (15 g) is reported with two significant figures, while the mass of NaCl (1.350 g) is reported with four significant figures. In addition, when you perform addition, the result should be reported to the precision of the least precise measurement, which in this case is 15 g (two significant figures). The sum, 16.350 g, must be rounded to two significant figures, which SAMPLEresults in 16 g. Thus, '16 g' reflects proper rounding and the appropriate significant figures based on the least precise measurement used in the addition, making it the rounded total mass of the combined substances.