Chemistry Class 9 Chapter 6 Important Questions Answers 2023
Chemistry Class 9
Chapter 6 ( Solutions )
Important Question/Answers
QUESTION.1
Define the terms:
A. Solution
B. Aqueous solution
C. Solute
D. Solvent
Answer
Solution
A homogenous mixture of two or more components with particles smaller than one nm is referred to as a solution.
Solutions come in many forms, including soda water, salt and sugar solutions, and others.
Every constituent in a solution appears as a single phase. The particles are homogeneous and form a uniform solution of the particles. Because of this, a bottle of soft drink has a consistent taste throughout.
Aqueous Solution
The Latin word “aqua” for water is the root of the English word “aqueous,” which implies “formed from, with, or by water.” Any substance that is referred to as aqueous is based on water. Aqueous is the general term used to describe both pure water (water devoid of dissolved compounds) and water-based solutions (water including dissolved things). Water is the solvent, and the things that dissolve in it to form an aqueous solution (such as sugar, salt, etc.) are referred to as solutes.
Solute
A solute dissolves in a solution. The amount of solvent present in fluid solutions is greater than the amount of solute.
A common example of a solute is glucose in water. Glucose is the solute present in a lesser amount of water (excess amount).
Solvent
A solvent is the component of a solution that is in excess. It is the fluid in which the solute has been dissolved. Typically, a solvent is a liquid.
Derived from the Latin term solv, which means “to loosen or untie,” is the source of the English word “solvent.”
QUESTION.2
What is a saturated solution and unsaturated solution and supersaturated solution?
ANSWER
Saturated Solution
A saturated solution is one that contains all of the solutes that can dissolve in it given the conditions in which it occurs. In chemistry, one may comprehend that a solution can attain a state of saturation by studying solutions and their properties of the solution. When there is no more solute left to dissolve, the solution has reached this state. A solid precipitate or gas would be released if more solutes were added after this point. A saturated solution is a name given to such a mixture.
Unsaturated Solution
Solutions that contain a relatively smaller amount of dissolved solute than the solvent’s saturation point are said to be unsaturated solutions (at that specific temperature). A solution is referred to as an unsaturated solution if the amount of dissolved solute is less than the solvent’s saturation point. Up to the point of saturation, unsaturated liquids can dissolve the additional solute. Unsaturated solutions are those in which the solvent has not reached the point at which no more solutes may be dissolved in it. As a result, it can be claimed that all solutions start out mainly unsaturated before becoming saturated when a solute is added to them.
Supersaturated Solution
By increasing the temperature of a saturated solution, adding more solute, and then slowly cooling it, one can form a supersaturated solution, which contains more solute than needed to create a saturated solution. By adding a few crystals of the solute to a supersaturated solution, extra dissolved solute crystallizes.
QUESTION .3
What is an example of gas in a gas solution?
ANSWER
Gas-Gas Solution
A gas-gas solution, also known as a solution in which a gaseous solute is dissolved in a gaseous solvent, includes air.
Multiple gases make up air.
- The solvent element nitrogen makes up about 78 percent of the air.
- At 20%, oxygen makes up the most solute in the atmosphere.
- Argon, carbon dioxide, neon, helium, and methane are among other solutes.
- Ozone, carbon monoxide, and ammonia are some examples of trace solutes, a uniform combination of several gases, including oxygen and nitrogen.
- Since it makes up the majority of the mixture, nitrogen is frequently referred to as the solvent and oxygen as the solute.
QUESTION .4
What is meant by a solution of liquids?
ANSWER
Solution of Liquids
A uniform mixture of a solvent and a solute is referred to as a liquid solution (there can be multiple solutes in the solvent). Since there is no precipitated material anywhere in the final solution, it is entirely liquid. Despite its liquid nature, the solution can contain both solids and gases.
An illustration would be to add methanol to a glass of water (H2O). Methanol will be equally dissolved by the water molecules throughout the solution, converting it to an aqueous state. A liquid solution would be the outcome.
The usual illustration uses:
- Water and ethanol
- Acetone and water
- Acetone with ethanol
- Hexane with benzene
- Toluene with diethyl ether
Any two liquids that are compatible with one another.
QUESTION .5
What are examples of solutions of solids in solids?
ANSWER
Solution of Solids
A homogenous mixture of two crystalline solids with comparable crystal lattices is referred to as a solid solution. Mixtures frequently include two or more types of atoms or molecules that share the same crystal lattice, much like certain metal alloys do.
Solvents are the most prevalent elements or compounds. Solid solutions are very prevalent.
Numerous alloys, ceramics, and polymer mixtures are reliable materials.
Brass is a solid solution made when copper and zinc combine to dissolve in one another and then harden.
Many diverse alloys with distinctive hues and looks are created from silver, gold, and copper. Solution of sodium chloride in water, sugar in water, and naphthalene in acetone are also prime examples of solutions of solids.
QUESTION .6
What do you mean by a concentration of a solution?
ANSWER
Concentration of Solution
The amount of solute that is dissolved in a specific amount of solvent or solution is measured by the solution’s concentration. A solution that contains a relatively higher amount of dissolved solute is said to be concentrated. This is a qualitative way of conveying how concentrated a solution is, and we usually talk about how diluted or concentrated a solution is. An extremely small amount of solute is present in a dilute solution, whereas a significant amount of solute is present in a concentrated solution. However, these are relative phrases that do not reveal the solution’s quantitative concentration.
QUESTION .7
What are the types of percentage solutions?
ANSWER
Percentage Solution
The percentage of a solute in the solvent is one way to express the concentration of a solution. The % can then be calculated in one of two ways:
(1) Using the ratio of the solute’s mass to that of the solution
(2) Using the solute’s volume to that of the solution
The percent solutions may take the following forms:
- weight/volume percentage
- volume/volume percentage
- weight/weight percentage
In each case, the volume or weight of the solute divided by the total volume or weight of the solution gives the concentration. It is also relevant to the numerator in weight units and the denominator in volume units and is known as weight/volume percent. This is true not only for a solution where concentration must be represented in volume percent (v/v% ) when the solute is a liquid.
Example
Concentration of H2SO4 is 98%
Concentration of HCl is 37%
If you dissolve 10g sodium chloride in 90g of water the concentration of solution is 10%
QUESTION .8
Write a note on molarity.
ANSWER
Molarity
Molarity (M), which is determined by dividing the solute’s mass in moles by the volume of the solution in liters, is the most widely used unit to express solution concentration: liters of solution/moles of solute equals M.
One liter of a solution with a 1.00 molar concentration (1.00 M) contains 1.00 moles of solute.
M, known as a molar, stands for molarity.
When one gram of solute dissolves in one litre of solution, the solution has a molarity of one. Since the solvent and solute combine to form a solution, the entire volume of the solution is measured.
EXAMPLE .1
A solution is prepared by bubbling 1.56 grams of hydrochloric acid in water. Here, the volume of the solution is 26.8 mL. Calculate the molarity of the solution.
Solution:
Formula of hydrochloric acid = HCl
Formula for Water = H2O
Molecular Mass of HCl = 35.5 ×1 + 1×1 = 36.5 moles/gram
Molecular Mass of H2O = 1 ×2 + 16 ×1 = 18 moles/gram
Given, mass of hydrochloric acid= 1.56 g
Number of moles of hydrochloric acid = mass in grams/molar mass= 1.56/36.5=4.27×10-2
Given volume of the solution = 26.8 ml
Expressing the volume in terms of litres = 2.68×10-2 litres
Molarity = moles of elements/ volume of solution
Molarity = 4.27×10-2 /2.68×10-2
Molarity = 1.59 M
EXAMPLE .2
If 2 gm NaOH is dissolute in water make a solution up to 250 cc. Give the molarity of the solution:
Solution
NaOH = W = 2 g
Molar Mass of NaOH = 23 + 16 + 1 = 40
M = W/M × 1000/(V ml) = 2/40 × 1000/250=1/5 M
EXAMPLE .3
Give the mass of NaOH dissolute to make a solution of 500 cm3, 1/2 M molar.
Solution
M = W/M × 1000/(V ml)
Molar Mass of NaOH = 23 + 16 + 1 = 40
M=1/2 and V=500 ml
Therefore,
1/2=W/40 ×1000/500
W=20/2=10gm
EXAMPLE .4
What is the molarity of 5.30 g of Na2CO3 dissolved in 400.0 mL solution?
Solution:
MV = grams / molar mass
(x) (0.4000 L) = 5.30 g / 105.988 g mol¯1
0.12501415 M
x = 0.125 M
EXAMPLE .5
How many moles of Na2CO3 are there in 10.0 L of 2.00 M solution?
Solution:
M = moles of solute/liters of solution
2.00 M = x / 10.0 L
x = 20.0 mol
QUESTION .9
What is the solubility of the solution?
ANSWER
Solubility
Solubility is the maximum amount of solute that dissolves in an exact volume of solvent at a particular temperature.
A homogenous mixture of one or more solutes in a solvent is referred to as a solution.
A typical illustration of a solution is the addition of sugar cubes to a cup of tea or coffee.
Solubility is a quality that aids in the dissolution of sugar molecules. Thus, the ability of a substance (solute) to dissolve in a specific solvent can be defined as solubility.
Any substance that is dissolved in a solvent and is either solid, liquid, or gas is referred to as a solute.
QUESTION .10
Write a note on solute-solvent interaction.
ANSWER
Solute Solvent Interactions
The famous and general rule for solute-solvent interaction is the saying Like dissolves Like.
Explanation
A solute’s interaction with a solvent result in the stabilization of the solute species in a solution. Insoluble materials can likewise be subject to the solvation interaction concept.
In theory, solvation and solubility are different. Solvation, another name for dissolution, is a kinetic process. The dynamic equilibrium state is known as solubility when the rate of precipitation and dissolution are equal. Solvation is influenced by van der Waals forces, hydrogen bonds, and bond formation. The act of dissolving a solute in water is known as hydration. Lattice energy and solvation, which includes entropy effects brought on by changes in the solvent structure, compete for control of solid-state solubility.
Example
Methanol dissolves in water due to hydrogen bonding. The bond formed between highly electronegative elements like F, O,N, and partially positive hydrogen is known as hydrogen bonding. The oxygen in methanol interacts with hydrogen from water to form hydrogen bonds and ultimately dissolve in water.
Glucose is also miscible in water due to hydrogen bonding.
Sodium chloride also dissolves in water due to the interaction of ions with polar elements of water.
On the other hand, organic species like butane, pentane, etc don’t dissolve in water ( inorganic nature) because of their inability to form hydrogen bonds and also the lack of ionic interaction.
QUESTION .11
What is the effect of temperature on solubility?
ANSWER
Solubility
Solubility is the maximum amount of solute that dissolves in an exact volume of solvent at a particular temperature
Effect Of Temperature
The vast majority of solids become more soluble as temperature rises. The impact, however, varies significantly from one solute to another and is challenging to anticipate. A solubility curve, or graph of the solubility vs. temperature, can be used to visualize how solubility changes with temperature
Take note of how NaCl’s temperature dependence is largely flat, indicating that a temperature rise has a negligible impact on the solubility of NaCl. On the other hand, the curve for KNO3 is extremely steep, increasing the solubility of KNO3 considerably as the temperature rises.
Several substances like HCl, NH3, and SO2 with the increase in temperature their solubility decreases. All of them are gases at atmospheric pressure. The kinetic energy of the solvent and the solute both rise when a solvent with a gas dissolved in it is heated. The molecules of the gaseous solute have a stronger propensity to resist the solvent molecules’ attraction and transition back to the gas phase as their kinetic energy rises. That is the prime reason because the solubility of gases decreases with increasing temperature.
QUESTION .12
Write a note on the following.
- Solution
- Colloids
- Suspension
ANSWER
Solution
A homogenous mixture of two or more components with particles smaller than one nm is referred to as a solution.
Solutions come in many forms, including soda water, salt and sugar solutions, and others. Every constituent in a solution appears as a single phase. The particles are homogeneous and form a uniform solution of the particles. Because of this, a bottle of soft drink has a consistent taste throughout.
Colloids
Colloids are mixtures in which small insoluble particles of a particular substance are suspended in another substance. They are also known as colloidal solutions. A colloid’s suspended particles might range anywhere from 1 and 1000 nanometers in size. A mixture must have suspended particles to be categorized as a colloid (in the manner that the particles of suspensions settle at the bottom of the container if left undisturbed). The Tyndall Effect, a phenomenon in which light beams incident on colloids are scattered as a result of interactions between the light and the colloidal particles, is known to occur in colloidal solutions. e.g.milk, butter, gelatin, jelly, fog.
Suspension
A heterogeneous solution is said to be a suspension if the solid particles are dispersed throughout the liquid without actually dissolving in it. A mixture of particles that are visible to the human eye and have a diameter larger than 1000 nm is referred to as a suspension.
Mud will create a heterogeneous combination if we mix it with water in a glass. The constituents of these mixes are simple to distinguish. After some time, we will see that the mud particles will gravitationally settle to the ground.
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