a) What is the name of the blood vessel that carries blood from heart to different parts of the body? [1] b) Write the name of compound which is formed when ammonia dissolves in water? [1] c) Why…

Here is the model answer for the given SEE 2081 (Science) question:

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a) Name of the blood vessel that carries blood from the heart to different parts of the body

The blood vessel that carries blood from the heart to different parts of the body is called an artery.

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b) Name of the compound formed when ammonia dissolves in water

When ammonia dissolves in water, it forms ammonium hydroxide (NH₄OH).

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c) Why carbon dioxide gas is collected in an erect gas jar

Carbon dioxide gas is denser than air (its density is about 1.98 kg/m³, whereas air is about 1.29 kg/m³). Therefore, it sinks and collects at the bottom of the jar. To collect it properly, the gas jar must be held erect (upright) to prevent the gas from escaping.

Carbon dioxideCarbon dioxide

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d) Precaution to be taken by a good netizen

A good netizen should:

• Respect others' privacy and avoid sharing personal information without consent.

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e) Change done by a negative catalyst in the rate of chemical reaction

A negative catalyst (inhibitor) decreases the rate of a chemical reaction by providing an alternative pathway with a higher activation energy.

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f) Reason why detergent is considered less eco-friendly than soap

Detergents contain phosphates and synthetic chemicals that do not biodegrade easily, leading to water pollution and harming aquatic life. Soap, on the other hand, is biodegradable and eco-friendly.

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g) Genotypic ratio at the second filial generation when black (Bb) and brown (bb) dogs are crossed

• Parental generation (P): Bb (black) × bb (brown)
• First filial (F₁) generation: All offspring are Bb (black) with a genotypic ratio of 100% Bb.
• Second filial (F₂) generation: When two F₁ dogs (Bb × Bb) are crossed, the genotypic ratio is:
  • 1 BB : 2 Bb : 1 bb (or 1:2:1).

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h) Ray diagram for the remedy of the student’s vision defect

The student is likely suffering from myopia (short-sightedness), where distant objects appear blurry. The remedy is to use a concave lens (diverging lens) to diverge the rays before they enter the eye, allowing them to focus properly on the retina.

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i) Calculation of the refractive index of water

Given:

• Speed of light in water ($v$) = $2.25\times 10^5\text{m/s}$
• Speed of light in air ($c$) = $3\times 10^8\text{m/s}$

The refractive index (n) of water is calculated using the formula: $$n=\frac{c}{v}$$

Substitute the values: $$n=\frac{3\times 10^8}{2.25\times 10^5}$$

$$n=\frac{3\times 10^8}{2.25\times 10^5}=\frac{3}{2.25}\times 10^{8-5}=1.33\times 10^3$$

$$n=1.33$$

Final answer: The refractive index of water is 1.33.

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