Question

1. calculate the number of grams of cucl₂·2h₂o needed to prepare 50 ml of 0.15 m stock solution. show your work in the space below.

Explanation:

Step1: Calculate moles of solute

Use the formula $n = M\times V$, where $M$ is molarity and $V$ is volume in liters. First, convert volume to liters: $V = 50\ mL=0.05\ L$, $M = 0.15\ M$. So $n = 0.15\ mol/L\times0.05\ L = 0.0075\ mol$.

Step2: Find molar mass of $CuCl_2\cdot2H_2O$

The molar mass of $Cu$ is approximately $63.55\ g/mol$, $Cl$ is approximately $35.45\ g/mol$, $H$ is approximately $1.01\ g/mol$ and $O$ is approximately $16.00\ g/mol$.
$M_{CuCl_2\cdot2H_2O}=63.55 + 2\times35.45+2\times(2\times1.01 + 16.00)=170.48\ g/mol$.

Step3: Calculate mass of solute

Use the formula $m=n\times M$. Substitute $n = 0.0075\ mol$ and $M = 170.48\ g/mol$. So $m=0.0075\ mol\times170.48\ g/mol = 1.2786\ g\approx1.28\ g$.

Answer:

$1.28\ g$