| # | Statement (Answer in bold) |
|---|---|
| 1 | The component present in lesser amount in a solution is called solute. |
| 2 | Example for liquid in solid type solution is mercury with silver (dental amalgam). |
| 3 | Solubility is the mass in grams of solute that dissolves in 100 g of solvent at a specified temperature. |
| 4 | Polar compounds are soluble in polar solvents. |
| 5 | Volume percentage decreases with increase in temperature because of thermal expansion of liquids. |
| Column A | Column B |
|---|---|
| Blue vitriol | CuSO4.5H2O |
| Gypsum | CaSO4.2H2O |
| Deliquescence | NaOH |
| Hygroscopic | CaO |
| # | Statement | Answer | Correction (if False) |
|---|---|---|---|
| 1 | Solutions which contain three components are called binary solution. | False | Solutions which contain three components are called ternary solutions. |
| 2 | In a solution the component which is present in lesser amount is called solvent. | False | The component present in lesser amount is called solute; solvent is present in larger amount. |
| 3 | Sodium chloride dissolved in water forms a non-aqueous solution. | False | Sodium chloride dissolved in water forms an aqueous solution. |
| 4 | The molecular formula of green vitriol is MgSO4.7H2O | False | The molecular formula of green vitriol is FeSO4.7H2O. |
| 5 | When silica gel is kept open, it absorbs moisture from the air, because it is hygroscopic in nature. | True |
A solution is defined as a homogeneous mixture of two or more substances. In a homogeneous mixture, the composition and properties are uniform throughout the mixture. This means that the solute particles are completely dissolved in the solvent, and they cannot be distinguished by the naked eye or even under a microscope. Examples include salt dissolved in water or sugar dissolved in water.
A binary solution is a solution that consists of only two components: one solute and one solvent. The solute is the substance that is dissolved, and the solvent is the substance in which the solute is dissolved. For instance, when sodium chloride (solute) is dissolved in water (solvent), it forms a binary solution. Most common solutions encountered are binary in nature.
(i) Gas in liquid: Carbon dioxide dissolved in water, as seen in carbonated beverages like soda water, is an example of a gas dissolved in a liquid. (ii) Solid in liquid: Sodium chloride (common salt) dissolved in water is a classic example of a solid dissolved in a liquid. (iii) Solid in solid: Alloys are solid solutions where one solid is dissolved in another. For example, gold with a small amount of copper dissolved in it forms an alloy, which is a solid in solid solution. (iv) Gas in gas: A mixture of gases, such as the air we breathe which is a mixture of nitrogen, oxygen, and other gases, or a specific mixture like helium and oxygen gases, represents a gas dissolved in a gas.
(i) An aqueous solution is a solution where water serves as the solvent. Water's ability to dissolve a wide variety of substances makes it a common solvent. Examples include common salt dissolved in water, sugar dissolved in water, or copper sulphate dissolved in water. (ii) A non-aqueous solution is one where the solvent is a liquid other than water. Many organic solvents are used for non-aqueous solutions. An example is sulphur dissolved in carbon disulphide, where carbon disulphide acts as the non-aqueous solvent.
$Volume Percentage = [ Volume of the solute / Volume of the solution ] * 100$
Aquatic animals typically thrive more in colder regions because cold water can dissolve a greater amount of dissolved oxygen compared to warm water. The solubility of gases, including oxygen, in liquids decreases as the temperature increases. Therefore, in colder environments, the water holds more dissolved oxygen, which is essential for the respiration and survival of aquatic organisms like fish.
A hydrated salt is a crystalline salt that incorporates a specific number of water molecules within its crystal structure. These water molecules are chemically bound to the salt ions and are referred to as water of crystallization. The number of water molecules is fixed and represented in the chemical formula. For example, copper sulphate pentahydrate (CuSO4.5H2O) is a hydrated salt containing five molecules of water of crystallization per formula unit of copper sulphate.
When a hot saturated solution of copper sulphate is cooled, crystals form because the solubility of copper sulphate decreases significantly with a decrease in temperature. A saturated solution at a high temperature contains the maximum amount of solute that can be dissolved. As the solution cools, it becomes supersaturated with respect to the lower temperature, and the excess dissolved copper sulphate can no longer remain in solution, causing it to precipitate out as solid crystals.
Given substances: concentrated sulphuric acid, copper sulphate pentahydrate, silica gel, calcium chloride and gypsum salt. Deliquescent substances are those that absorb so much moisture from the atmosphere that they eventually dissolve in the absorbed water to form a solution. From the given list, calcium chloride is a deliquescent substance. Hygroscopic substances are those that absorb moisture from the atmosphere but do not dissolve in it. Concentrated sulphuric acid and silica gel are hygroscopic. Copper sulphate pentahydrate and gypsum are hydrated salts, which contain water of crystallization but do not actively absorb moisture from the air in the same way as deliquescent or hygroscopic substances.
(i) A saturated solution is a solution in which the maximum amount of solute has been dissolved in a given amount of solvent at a specific temperature. At this point, the rate of dissolution of solute equals the rate of crystallization of solute, and no more solute can be dissolved under these conditions. An example is 36 grams of sodium chloride dissolved in 100 grams of water at 25°C, which forms a saturated solution. (ii) An unsaturated solution is a solution that contains less solute than the maximum amount that can be dissolved in the solvent at a given temperature. In an unsaturated solution, more solute can still be dissolved without reaching the saturation point. For instance, if 10 grams, 20 grams, or 30 grams of sodium chloride are dissolved in 100 grams of water at 25°C, these would all be unsaturated solutions.
Nature of solute and solvent: Solubility follows "like dissolves like". Polar compounds dissolve in polar solvents, for example common salt dissolves in water. Non-polar compounds dissolve in non-polar solvents, for example sulphur dissolves in carbon disulphide.
Temperature: Generally, the solubility of a solid in a liquid increases with increase in temperature. In endothermic dissolution, solubility increases with temperature; in exothermic dissolution, it decreases. The solubility of gases in liquids decreases with increase in temperature.
Pressure: When pressure is increased, the solubility of a gas in a liquid increases because more gas molecules strike and enter the liquid surface.
MgSO4.7H2O (s) -> MgSO4 (s) + 7H2O (g)
b) Solubility is the number of grams of solute that can dissolve in 100 g of solvent to form a saturated solution at a given temperature.
$Solubility = [ Mass of the solute / Mass of the solvent ] \times 100$
Hygroscopic substances and deliquescent substances both absorb moisture from the atmosphere, but they differ in their behavior and the extent of absorption. Deliquescent substances are typically water-soluble solids that absorb atmospheric moisture to such an extent that they dissolve in the absorbed water, forming a solution or a paste. They often change their physical state from solid to liquid upon exposure to air. Examples include calcium chloride and sodium hydroxide. Hygroscopic substances, on the other hand, absorb moisture from the atmosphere but do not necessarily dissolve in it. They may become moist or sticky, but they retain their solid or liquid form without forming a solution. Examples include concentrated sulfuric acid, silica gel, and phosphorus pentoxide. Essentially, deliquescence is a more extreme form of hygroscopy where the substance liquefies.
$= [ Mass of the solute / (Mass of the solute + Mass of the solvent)] \times 100$
$= [ 45 / (45+180)] \times 100 = 45 / 225 \times 100$
$Mass percentage = 20%$
$= [3.5 / 15] \times 100$
$= 23.33%$
Vinu will get faster dissolution of sugar. This is because Vinu is dissolving sugar in hot water, while Sarath is dissolving it in cold water. The rate of dissolution of a solid solute in a liquid solvent is generally higher at higher temperatures. This is due to increased kinetic energy of the solvent molecules, which leads to more frequent and energetic collisions with the solute particles, breaking them apart and dispersing them more rapidly. Therefore, hot water facilitates a quicker dissolving process for sugar compared to cold water.
CuSO4.5H2O (blue) --heat-> CuSO4 (white) + 5H2O
When water is added, anhydrous copper sulphate becomes blue hydrated copper sulphate again:
CuSO4 (white) + 5H2O -> CuSO4.5H2O (blue)
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