Question

A student measures out 35g of NaCl. How many moles did he measure?

A) 2.1 x 10^25
B) 1.7
C) .6
D) 1.7 x 10^22

Answer 1

Using the molar mass of NaCl (58.44 g/mol), 35g of NaCl can be converted to moles by dividing the mass by the molar mass, resulting in approximately 0.6 moles of NaCl.

Step-by-step explanation:

To determine how many moles of NaCl the student measured out when they have 35g of NaCl, you need to use the molar mass of NaCl as a unit conversion factor. The molar mass of NaCl is 58.44 g/mol, which is the sum of the atomic masses of sodium (Na, approximately 23.0 u) and chlorine (Cl, approximately 35.5 u).

Step 1: Convert from grams to moles of NaCl using the molar mass of NaCl in the unit conversion factor.

• Number of moles (mol) = mass (g) / molar mass (g/mol)
• Number of moles = 35g / 58.44 g/mol
• Number of moles = 0.599 moles of NaCl, which can be rounded to 0.6 moles.

Therefore, the student has measured out approximately 0.6 moles of NaCl. The correct answer from the given options is C) .6.