NCEA Level 3 Chemistry – Aqueous Chemistry (AS91393) Practice Exam

To determine how many grams of NaCl (sodium chloride) are needed to make a 1 M solution in 1 liter of water, we need to understand the concept of molarity (M). Molarity is defined as moles of solute per liter of solution. A 1 M solution means there is 1 mole of solute (in this case, NaCl) per liter of solution.

To find out the number of grams needed, we start with the molar mass of NaCl. Sodium (Na) has an atomic mass of approximately 23.00 g/mol, and chlorine (Cl) has an atomic mass of about 35.45 g/mol. When you add these together, the total molar mass of NaCl becomes:

\[

\text{Molar mass of NaCl} = 23.00 \, \text{g/mol (Na)} + 35.45 \, \text{g/mol (Cl)} = 58.44 \, \text{g/mol}

\]

Since we need to prepare a 1 M solution, this implies that we need 1 mole of NaCl in 1 liter of water. Therefore, to achieve a 1 M concentration