How many grams of HCl are needed to make 200.0 mL of a 3.0 M solution?
HCI: 36.46 g/mol
Answer (2)
To make 200.0 mL of a 3.0 M HCl solution, you need about 21.876 grams of HCl. This is calculated by converting the volume to liters, determining moles from molarity, and then finding the mass using the molar mass of HCl. Therefore, 21.876 grams is the required amount.
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Convert the volume from mL to L: V L = 1000 200.0 = 0.2 L .
Calculate the number of moles of HCl: n = 3.0 M × 0.2 L = 0.6 moles .
Calculate the mass of HCl: mass = 0.6 moles × 36.46 mol g = 21.876 g .
The mass of HCl needed is 21.876 g .
Explanation
Problem Analysis We are given the volume and molarity of an HCl solution, and we need to find the mass of HCl required to prepare the solution. Let's break down the problem and solve it step by step.
Volume Conversion First, we need to convert the volume from milliliters (mL) to liters (L) since molarity is defined as moles per liter. To convert 200.0 mL to liters, we divide by 1000: V L = 1000 V m L = 1000 200.0 = 0.2 L
Calculating Moles of HCl Next, we calculate the number of moles of HCl needed using the formula: n = M × V L where n is the number of moles, M is the molarity (3.0 M), and V L is the volume in liters (0.2 L). n = 3.0 M × 0.2 L = 0.6 moles
Calculating Mass of HCl Now that we know the number of moles of HCl needed, we can calculate the mass of HCl using the molar mass of HCl (36.46 g/mol). The formula is: mass = n × MM where mass is the mass in grams, n is the number of moles (0.6 moles), and MM is the molar mass (36.46 g/mol). mass = 0.6 moles × 36.46 mol g = 21.876 g
Final Answer Therefore, 21.876 grams of HCl are needed to make 200.0 mL of a 3.0 M solution.
Examples
In a chemistry lab, you often need to prepare solutions of specific concentrations for experiments. For example, you might need to create a hydrochloric acid (HCl) solution to adjust the pH of a reaction mixture. Knowing how to calculate the mass of solute needed to achieve a desired molarity is crucial for accurate and reproducible results. This calculation ensures that your experiments are conducted with the correct concentrations, leading to reliable data and valid conclusions.
