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Which of the following statements are correct for pure substances? (i) Pure substances contain only one kind of particles. (ii) Pure substances may be compounds or mixtures. (iii) Pure substances have the same composition throughout. (iv) Pure substances can be exemplified by all elements other than copper. (a) (i) and (ii) (b) (i) and (iii) (c) (iii) and (iv) (d) (ii) and (iii)
The correct answer is: (b) (i) and (iii). Pure substances contain only one kind of particles, either atoms or molecules. Pure substances have a uniform composition throughout. https://www.tiwariacademy.com/ncert-solutions/class-9/science/chapter-2/
The correct answer is: (b) (i) and (iii).
Pure substances contain only one kind of particles, either atoms or molecules.
Pure substances have a uniform composition throughout.
https://www.tiwariacademy.com/ncert-solutions/class-9/science/chapter-2/
See lessTwo substances A and B were made to react to form a third substance A₂B according to the following reaction: 2A + B → A₂B Which of the following statements concerning this reaction are incorrect? (i) The product A₂B shows the properties of the substances A and B. (ii) The product will always have a fixed composition. (iii) The product so formed cannot be classified as a compound. (iv) The product so formed is an element. (a) (i), (ii) and (iii) (b) (i), (ii) and (iv) (c) (i), (iii) and (iv) (d) (ii), (iii) and (iv)
The correct answer is: (c) (i), (iii), and (iv) (i) Incorrect – The product A₂B is a new substance with different properties from A and B. (ii) Correct – Compounds always have a fixed composition. (iii) Incorrect – A₂B is a compound because it is formed by the chemical combination of A and B. (iv) IRead more
The correct answer is: (c) (i), (iii), and (iv)
(i) Incorrect – The product A₂B is a new substance with different properties from A and B.
(ii) Correct – Compounds always have a fixed composition.
(iii) Incorrect – A₂B is a compound because it is formed by the chemical combination of A and B.
(iv) Incorrect – A compound is different from an element; A₂B is not an element.
https://www.tiwariacademy.com/ncert-solutions/class-9/science/chapter-2/
See lessThe acute angle which the line with direction cosines 1/√ 3, 1/√ 6, n makes with positive direction of z-axis is
The direction cosines of the line are given as: l = 1/√3, m = 1/√6, n = n The angle θ that the line makes with the positive z-axis is related to the direction cosine n by: cos θ = n To find the acute angle, we need to calculate the value of n using the condition that the sum of the squares of the diRead more
The direction cosines of the line are given as:
l = 1/√3, m = 1/√6, n = n
The angle θ that the line makes with the positive z-axis is related to the direction cosine n by:
cos θ = n
To find the acute angle, we need to calculate the value of n using the condition that the sum of the squares of the direction cosines equals 1:
l² + m² + n² = 1
Substituting the values of l and m:
(1/√3)² + (1/√6)² + n² = 1
1/3 + 1/6 + n² = 1
1/2 + n² = 1
n² = 1/2
n = 1/√2
Thus, cos θ = 1/√2, which gives: θ = π/4
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A few substances are arranged in the increasing order of forces of attraction between their particles. Which one of the following represents a correct arrangement ? (a) Water, air, wind (b) Air, sugar, oil (c) Oxygen, water, sugar (d) Salt, juice, air
(c) Oxygen, water, sugar In matter, the force of attraction between particles increases from gases to liquids to solids. Oxygen (gas) has the weakest forces, water (liquid) has moderate forces, and sugar (solid) has the strongest intermolecular forces. https://www.tiwariacademy.com/ncert-solutions/cRead more
(c) Oxygen, water, sugar
In matter, the force of attraction between particles increases from gases to liquids to solids. Oxygen (gas) has the weakest forces, water (liquid) has moderate forces, and sugar (solid) has the strongest intermolecular forces.
https://www.tiwariacademy.com/ncert-solutions/class-9/science/chapter-1/
See lessThe boiling points of diethyl ether, acetone and n-butyl alcohol are 35 °C, 56 °C and 118 °C respectively. Which one of the following correctly represents their boiling points in kelvin scale? (a) 306 K, 329 K, 391 K (b) 308 K, 329 K, 392 K (c) 308 K, 329 Κ, 391 Κ (d) 329 K, 392 Κ, 308 K
(c) 308 K, 329 K, 391 K. To convert Celsius to Kelvin: K = °C + 273 Diethyl ether: 35°C + 273 = 308 K Acetone: 56°C + 273 = 329 K n-Butyl alcohol: 118°C + 273 = 391 K https://www.tiwariacademy.com/ncert-solutions/class-9/science/chapter-1/
(c) 308 K, 329 K, 391 K.
To convert Celsius to Kelvin:
K = °C + 273
Diethyl ether: 35°C + 273 = 308 K
Acetone: 56°C + 273 = 329 K
n-Butyl alcohol: 118°C + 273 = 391 K
https://www.tiwariacademy.com/ncert-solutions/class-9/science/chapter-1/
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