Question

Define Molarity. Calculate Molarity of a 3L aqueous solution containing 18g of Glucose. *


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Answer 1

Molarity is defined as the number of moles of solute dissolved in 1 L volume of solution.

${\boxed{\sf{Molarity = {\dfrac{no. \ of \ moles \ of \ solute}{volume \ of \ solution \ (in \ L)}}}}}$

Calculate molarity of 3 L aqueous solution containing 18 g of glucose.

Here, glucose acts as solute and its chemical formula is C₆H₁₂O₆

Given mass of glucose = 18 g

Molar mass of glucose = $\sf{6m_C + 12m_H + 6m_O}$

                                      = 6(12) + 12(1) + 6(16)

                                      = 72 + 12 + 96

                                      = 180 g/mol

Number of moles of solute, glucose = $\sf{ {\dfrac{Given \ mass}{Molar \ mass}} }$

                                                            = 18/180 = 0.1 mol

Volume of solution = 3 L

• Putting all these values in the above written formula.

$\longrightarrow\sf{ {\dfrac{0.1}{3}} }$

$\longrightarrow$ 0.03 mol L⁻¹