Volumetric Analysis and Concentrations
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Questions and Answers

A titration is a laboratory procedure where a measured volume of one solution is added to a known volume of another solution until the reaction is ______.

complete

The ______ flask is designed to contain a definite volume of solution.

volumetric

The last few cm3 of water must be added carefully so that the bottom of the meniscus rests on the ______ mark.

calibration

A ______ is used to deliver an exact volume of solution.

<p>pipette</p> Signup and view all the answers

Before use, graduated cylinders should always be rinsed with ______ water.

<p>deionised</p> Signup and view all the answers

The liquid is allowed to run into a beaker until the bottom of the ______ is level with the graduation mark.

<p>meniscus</p> Signup and view all the answers

A solution is a completely perfect mixture of a ______ and a solvent.

<p>solute</p> Signup and view all the answers

The tip of the pipette is touched against the side of a glass ______ to remove the drop adhering to the tip.

<p>beaker</p> Signup and view all the answers

The concentration of a solution is the amount of ______ that is dissolved in a given volume of solution.

<p>solute</p> Signup and view all the answers

It is allowed to discharge slowly into a ______ flask, keeping the tip of the pipette in contact with the side.

<p>conical</p> Signup and view all the answers

10% NaCl w/w means that there are 10 g of sodium chloride per 100 g of ______.

<p>solution</p> Signup and view all the answers

Before use, the pipette should be rinsed with ______ water to remove contaminants.

<p>deionised</p> Signup and view all the answers

The conical flask should not be washed out with the ______ it is to contain.

<p>solution</p> Signup and view all the answers

1 ppm is equivalent to 1 mg of solute per million ______.

<p>mg</p> Signup and view all the answers

To standardise hydrochloric acid solution, approximately 50 cm3 of the ______ acid solution is poured into a clean dry beaker.

<p>hydrochloric</p> Signup and view all the answers

The molarity of a solution is the number of moles of solute per litre of ______.

<p>solution</p> Signup and view all the answers

When filling the burette, ensure that there are no air ______ in the nozzle.

<p>bubbles</p> Signup and view all the answers

0.85% w/v means that there are 0.85 g NaCl per 100 cm3 of the ______.

<p>solution</p> Signup and view all the answers

A 1 M (one molar) solution contains one mole of the solute dissolved in one litre of ______.

<p>solution</p> Signup and view all the answers

Add 2-3 drops of ______ orange indicator to the sodium carbonate solution in the conical flask.

<p>methyl</p> Signup and view all the answers

To make a 0.85% w/v solution of NaCl, you would need to dissolve ______ g of NaCl in 250 cm3 of solution.

<p>2.125</p> Signup and view all the answers

White crystals are formed in the ______ dish.

<p>evaporating</p> Signup and view all the answers

To determine the concentration of ______ in vinegar.

<p>ethanoic acid</p> Signup and view all the answers

Add 3 drops of ______ indicator to the conical flask.

<p>phenolphthalein</p> Signup and view all the answers

At the end point, the phenolphthalein changes from pink to ______.

<p>colourless</p> Signup and view all the answers

Weigh accurately approximately ______ g of hydrated sodium carbonate into a beaker.

<p>1.5</p> Signup and view all the answers

Titrate the sodium carbonate solution against ______ M hydrochloric acid.

<p>0.1</p> Signup and view all the answers

Methyl orange changes from yellow to ______ at the end point.

<p>red/pink</p> Signup and view all the answers

A batch of washing soda crystals had lost some of its water by a process called ______.

<p>efflorescence</p> Signup and view all the answers

A chemist was required to determine the percentage water of ______ in the crystals.

<p>crystallisation</p> Signup and view all the answers

The mean volume of the hydrochloric acid solution required to reach the ______ was 21.6 cm3.

<p>end point</p> Signup and view all the answers

A number of 25.0 cm3 portions of this solution were titrated with a previously ______ hydrochloric acid solution.

<p>standardised</p> Signup and view all the answers

The balance equation for the titration reaction is: 2HCl + Na2CO3 → 2NaCl + H2O + ______.

<p>CO2</p> Signup and view all the answers

To calculate the concentration of sodium carbonate, the volume and molarity of the ______ solution are used.

<p>HCl</p> Signup and view all the answers

The chemist should have added the sample to a ______ of deionised water to dissolve it properly.

<p>beaker</p> Signup and view all the answers

Add the hydrochloric acid drop by ______ to accurately detect the end point of the titration.

<p>drop</p> Signup and view all the answers

The formula for hydrated sodium carbonate is Na2CO3.x H2O, where x represents the number of ______ molecules.

<p>water</p> Signup and view all the answers

The balanced equation for the titration reaction indicates that 2 moles of hydrochloric acid react with 1 mole of ______.

<p>sodium carbonate</p> Signup and view all the answers

To prepare a 0.05 M primary standard solution, the student must accurately measure a known mass of pure anhydrous ______.

<p>sodium carbonate</p> Signup and view all the answers

The exact mass of anhydrous sodium carbonate required to prepare the solution was calculated to be ______ grams.

<p>2.65</p> Signup and view all the answers

The indicator used for this titration is ______, which changes from orange to red at the end point.

<p>Methyl Orange</p> Signup and view all the answers

The mean titre during the titration was measured to be ______ cm3.

<p>20.8</p> Signup and view all the answers

The student used a pipette filler to avoid the solution getting into their ______ for hygiene reasons.

<p>mouth</p> Signup and view all the answers

The concentration of hydrochloric acid solution can be calculated by using the formula ______.

<p>Va x Ma = Vb x Mb</p> Signup and view all the answers

Flashcards

Titration

A lab procedure where a specific amount of one solution is added to another until the reaction is complete.

Graduated Cylinder

Used to measure approximate volumes of liquids, not precise measurements.

Volumetric Flask

Used to create a precise volume of solution.

Pipette

Used to transfer exact volumes of solution.

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Meniscus

The curved upper surface of a liquid.

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Solution Concentration (Definition)

Amount of solute dissolved in a given volume of solution.

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Percentage Concentration (w/w)

Grams of solute per 100 grams of solution.

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Percentage Concentration (w/v)

Grams of solute per 100 cm³ of solution.

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Percentage Concentration (v/v)

Volume of solute per 100 cm³ of solution.

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Parts per Million (ppm)

1 milligram of solute per 1 liter of solution.

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Molarity (Definition)

Moles of solute per liter of solution.

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1M Solution

Contains one mole of solute per one liter of solution.

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Converting Moles/Liter to Grams/Liter

Calculate the amount of solute (grams) in a given volume of solution given its concentration (moles/liter) using the molar mass of the solute.

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Pipette Filler Use

Used to draw and dispense liquid into a container with accuracy.

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Pipette Tip Placement

Touch the pipette tip against the container's side to remove adhering drop and discharge solution slowly.

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Conical Flask Purpose

Designed for swirling solutions without spilling, and removing droplets from sides for better mixing.

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Burette Rinse Process

Rinse burette with deionized water initially, then solution for accurate transfers, eliminating water residue.

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Burette Use (0 Mark)

Fill burette with acid above the zero mark, adjust tap to precisely reach zero mark in the container, ensuring no air bubbles present.

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Meniscus Observation

Record the liquid level in the burette by reading the bottom of the concave meniscus line at eye level, which is important for precision.

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Pipette Rinse Procedure

Rinse the pipette with deionized water, then sodium carbonate solution to remove all traces of water before transferring to conical flask.

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Conical Flask Cleaning

Clean the conical flask with deionized water, avoiding cleaning procedures with the solution the chemicals need to react with.

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Efflorescence

The loss of water of crystallization from a hydrated salt, resulting in a change in the crystal's appearance and structure.

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Hydrated Salt

A salt that contains water molecules within its crystal structure.

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Water of Crystallization

The number of water molecules associated with each formula unit of a hydrated salt.

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What is a titration?

A technique used to determine the concentration of a solution by reacting it with a solution of known concentration.

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What is the purpose of a burette?

A graduated glass tube used to deliver precise volumes of liquid during a titration.

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What is the purpose of a pipette?

A glass tube used to transfer precise volumes of liquid.

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What is the purpose of an indicator?

A substance that changes color to signal the endpoint of a titration.

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What is the endpoint of a titration?

The point at which the indicator changes color, indicating the completion of the reaction between the solutions.

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Standard Solution

A solution whose exact concentration is known. It's used to determine the concentration of an unknown solution through titration.

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Dissolving Washing Soda Crystals

The process of dissolving a weighed sample of washing soda crystals in deionized water to create a specific volume of solution.

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Precaution During Titration

Adding the titrant drop-wise near the endpoint to ensure accurate measurement. This minimizes the risk of overshooting the endpoint, leading to inaccurate results.

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Suitable Indicator

A substance used to visually signal the endpoint of a titration reaction. The indicator changes color when the reaction is complete.

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Calculating Concentration (Moles/L)

Determining the number of moles of solute per liter of solution. The unit of concentration is moles per liter (mol/L) or molarity.

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Calculating Concentration (g/L)

Expressing the concentration of a solution in terms of grams of solute per liter of solution.

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Percentage Water of Crystallisation

The percentage by mass of water molecules present in a hydrated compound. This helps determine the ratio of water molecules in the compound's formula.

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Average Number of Water Molecules

Representing the average number of water molecules associated with each formula unit of a hydrated compound. This value is denoted by 'x' in the formula Na2CO3.xH2O.

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Primary Standard Solution

A pure, stable, and soluble substance used to prepare solutions of accurately known concentrations.

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Anhydrous

A substance that does not contain water molecules.

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How to prepare a standard solution

To prepare a standard solution, dissolve a known mass of the primary standard in a specific volume of solvent. The solution's concentration can be determined by calculating the moles of solute per unit volume.

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Why is a pipette filler used?

A pipette filler is used to avoid drawing the solution into the mouth, ensuring safety and hygiene.

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End Point in Titration

The point in titration where the indicator changes colour, indicating that the reaction is complete.

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Methyl Orange Indicator

A chemical indicator used in titration that changes color from orange to red at the end point.

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Calculation of Concentration

The concentration of a solution can be calculated using titration data and the balanced chemical equation. Concentration can be expressed in moles per liter (M) or grams per liter (g/L).

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Study Notes

Volumetric Analysis

  • Volumetric analysis is a quantitative method using solution reactions
  • Solutions react with each other, used to determine concentrations of solutions accurately.

Expressing Concentrations of Solutions

  • Solution: A perfect mixture of solute and solvent (homogeneous)
  • Concentration: Amount of solute dissolved in a given volume of solution.
  • Different ways to express concentration:

Percentage of Solute

  • Weight per weight (w/w): Grams of solute per 100 grams of solution (g/100g)
    • Example: 10% NaCl w/w means 10g NaCl in 100g solution
  • Weight per volume (w/v): Grams of solute per 100 cm³ of solution (g/100cm³)
    • Example: 10% w/v NaCl means 10g NaCl in 100 cm³ solution
  • Volume per volume (v/v): Volume of solute per 100 cm³ of solution (cm³/100cm³)
    • Example: 10% v/v ethanol means 10 cm³ ethanol in 100 cm³ solution

Moles of Solute per Litre (Molarity)

  • Molarity: Moles of solute per litre of solution (M)
    • 1M solution contains 1 mole of solute in 1 litre of solution.
  • Convert between moles/litre and grams/litre using molar mass.

Parts per Million (ppm)

  • Used for very dilute solutions
  • 1 ppm = 1 mg/L

Dilution of Solutions

  • Number of moles of solute remains constant during dilution.
  • M1V1 = M2V2 (where M1 and V1 are initial molarity and volume, and M2 and V2 are final molarity and volume).

Titrations

  • Procedure to measure the exact volume of one solution that reacts completely with a known volume of a second solution.

Standard Solutions

  • Solutions with known concentrations.
  • Primary standard solutions are pure, stable, easily soluble, and have a high molar mass, and undergo complete and rapid reactions.

Reaction Between a Solution and a Solid

  • Calculate the mass of Mg that reacts with a given volume and concentration of sulfuric acid (H2SO4).

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Volumetric Analysis PDF

Description

Test your knowledge on volumetric analysis and the various ways to express concentrations of solutions. This quiz covers percentage calculations and molarity concepts, essential for understanding solution chemistry. Enhance your skills in quantitative chemical analysis today!

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