Question

solve the following concentration questions
a) how many moles of cuso₄ are required to prepare 3.0 l of a 1.8 m solution?
b) how many liters of a 0.500 m nacl solution are needed to provide 2.5 moles of nacl?
c) calculate the molarity of a solution containing 8.0 g of koh dissolved to form 0.500 l of solution.
d) what volume of solution, in liters, is required to prepare a 2.0 m solution if 10.0 g of ba(no₃)₂ is dissolved?
e) what mass, in grams, of na₂so₄ will be required to prepare 1.5 l of 1.0 m solution?
f) how many moles of hcl are in 3000 ml of a 15.0% hcl solution?

Explanation:

Part (a)

Step1: Recall Molarity Formula

Molarity ($M$) is defined as moles of solute ($n$) divided by volume of solution in liters ($V$), so $M=\frac{n}{V}$. We need to find $n$, so rearrange to $n = M\times V$.

Step2: Substitute Values

Given $M = 1.8\ M$, $V = 3.0\ L$. Then $n=1.8\ M\times3.0\ L = 5.4\ mol$.

Step1: Rearrange Molarity Formula

From $M=\frac{n}{V}$, solve for $V$: $V=\frac{n}{M}$.

Step2: Substitute Values

Given $n = 2.5\ mol$, $M = 0.500\ M$. Then $V=\frac{2.5\ mol}{0.500\ M}=5.0\ L$.

Step1: Calculate Moles of KOH

Molar mass of $KOH$: $K(39.10)+O(16.00)+H(1.01)=56.11\ g/mol$. Moles $n=\frac{mass}{molar\ mass}=\frac{8.0\ g}{56.11\ g/mol}\approx0.1426\ mol$.

Step2: Use Molarity Formula

$M=\frac{n}{V}$, $V = 0.500\ L$. So $M=\frac{0.1426\ mol}{0.500\ L}\approx0.285\ M$.

Answer:

$5.4$ moles

Part (b)