Which of the following is not an “element + element → compound” type reaction?
a.
C(s) + O2(g) → CO2(g)
b.
2K(s) + Br2(l) → 2KBr(s)
c.
2CO(g) + O2(g) → 2CO2(g)
Correct Answer
d.
4Fe(s) + 3O2(g) → 2Fe2O3(s)
Step-by-Step AI Explanation
Verified Method
The reaction in option C is not an element + element → compound type reaction because CO is a compound, not an element. Here, a compound reacts with oxygen to form another compound. Options A, B, and D are all combinations of two elements forming a compound.
Q12mcq
Cancer of the epithelial cell is called as __________.
a.
Leukaemia
b.
Sarcoma
c.
Carcinoma
Correct Answer
d.
Lipoma
Step-by-Step AI Explanation
Verified Method
Cancer of epithelial cells is called carcinoma. Leukaemia is cancer of blood-forming tissues, sarcoma arises from connective tissues, and lipoma is a benign tumour of fat tissue.
Q13short answer2 marks
What is coefficient of apparent expansion ?
Step-by-Step AI Explanation
Verified Method
The coefficient of apparent expansion is the apparent increase in volume of a liquid per unit original volume per degree rise in temperature. It is given by
$$\gamma_a = \frac{\text{apparent increase in volume}}{V_0\,\Delta T}$$
where $V_0$ is the original volume and $\Delta T$ is the rise in temperature.
Q14short answer2 marks
Why is tungsten metal used in bulbs but not used as fuse wires ?
Step-by-Step AI Explanation
Verified Method
Tungsten is used in bulbs because it has a very high melting point and can withstand the high temperature produced when current passes through it. It is not used as fuse wire because a fuse wire should have a low melting point so that it melts quickly and breaks the circuit during excess current.
Q14long answer
Write any three features of natural and artificial radioactivity.
Step-by-Step AI Explanation
Verified Method
Any three features of natural and artificial radioactivity are:
1. Natural radioactivity is a spontaneous process, whereas artificial radioactivity is induced by bombarding a stable nucleus with suitable particles.
2. In both natural and artificial radioactivity, unstable nuclei emit alpha, beta, or gamma radiations to become more stable.
3. Both processes are nuclear phenomena and are not affected by physical or chemical changes such as temperature, pressure, or chemical combination.
4. Natural radioactivity occurs in naturally occurring elements like uranium and radium, while artificial radioactivity is produced in the laboratory.
Q15short answer
Name any two devices, which are working on the heating effect of current.
Step-by-Step AI Explanation
Verified Method
Two devices that work on the heating effect of electric current are:
1. Electric iron
2. Electric heater
Q15short answer2 marks
What is rust ? Give the equation for the formation of rust.
Step-by-Step AI Explanation
Verified Method
Rust is the reddish-brown hydrated iron(III) oxide formed on iron when it reacts with oxygen and water. The equation for rust formation is:
$$4Fe + 3O_2 + xH_2O \rightarrow 2Fe_2O_3\cdot xH_2O$$
Q16short answer
What happens when $\mathrm{MgSO_4\cdot7H_2O}$ is heated? Write the appropriate equation.
Step-by-Step AI Explanation
Verified Method
When $\mathrm{MgSO_4 \cdot 7H_2O}$ is heated, it loses its water of crystallisation and forms anhydrous magnesium sulphate.
$$\mathrm{MgSO_4 \cdot 7H_2O \xrightarrow{heat} MgSO_4 + 7H_2O}$$
Q16short answer2 marks
What is stage ?
Step-by-Step AI Explanation
Verified Method
A stage is a level in the food chain. It represents one step or position occupied by an organism in the transfer of energy from producers to consumers.
Q17short answer
Why is sinoatrial node called as pacemaker of heart?
Step-by-Step AI Explanation
Verified Method
The sinoatrial node is called the pacemaker of the heart because it generates regular electrical impulses on its own and initiates each heartbeat. It controls the rate and rhythm of the heart.
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Under same conditions of temperature and pressure, if you collect 3 litre of $O_2$, 5 litre of $Cl_2$ and 6 litre of $H_2$, (A)Which has the highest number of molecules ? (B)Which has the lowest number of molecules ?
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An organic compound ‘A’ is widely used as a preservative and has the molecular formula $C_2H_4O_2$. This compound reacts with ethanol to form a sweet smelling compound ‘B’, then (A)Identify the compound ‘A’. (B)Write the chemical equation for its reaction with ethanol to form compound ‘B’. (C)Name this process.
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