37
Q:

# An atom has 7 electrons in its M - shell and contains 18 neutrons in its nucleus. What is its mass number

 A) 25 B) 27 C) 35 D) 43

Explanation:

According to Bohr model, Each shell can occupy 2$n2$ electrons in their orbits where n=1,2,3.. for K,L,M,..

The atom has 2 electrons in k, 8 electrons in L and 7 electrons in M = 2 + 8 + 7 = 17

And given that its nucleus has 18 neutrons

=> its mass number = number of (electrons + neutrons ) = 17 + 18 = 35

Subject: Chemistry
Q:

In the thermite process, the reducing agent is

 A) Chlorine B) Aluminium C) Silicon D) Iron

Explanation:

In the thermite process, the reducing agent is Aluminium.

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0 101
Q:

In which of the following activities silicon carbide is used

 A) Disinfecting water of ponds B) Making casts for statues C) Making cement and glass D) Cutting very hard substances

Explanation:

Silicon carbide is used in Cutting very hard substances.

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0 106
Q:

Which is a compound that contains carbon?

 A) Ethane B) Propane C) Methane D) All of the above

Explanation:

The compound methane is a simple hydrocarbon contains one carbon bonded to four hydrogens. Ethane is a simple hydrocarbon which contains two carbon atoms and four hydrogen atoms. Similarly, propane with three carbons.

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1 101
Q:

The main use of salt in the diet is to

 A) produce in small amounts the hydrochloric acid required for the digestion of food B) increase the solubility of food particles in water C) make the taste of food better D) ease the process of cooking

Answer & Explanation Answer: A) produce in small amounts the hydrochloric acid required for the digestion of food

Explanation:

The main use of salt in the diet is to produce in small amounts the hydrochloric acid required for the digestion of food.

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1 178
Q:

The most electronegative element among the following is

 A) Oxygen B) Chlorine C) Nitrogen D) Sodium

Explanation:

Electronegativity measures an element's ability to form chemical bonds. Helium is the most electronegative element followed by Fluorine.

Here in the given options, Oxygen is the most electronegative element. Fluorine is followed by Oxygen, Chlorine and Nitrogen is the most electronegative elements list.

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1 178
Q:

Bullet proof material is made up of which polymer?

 A) Poly carbonates B) Poly vinyl C) Poly amides D) Polychloride

Explanation:

bullet proof material is made up of polymer Poly carbonates.

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1 194
Q:

The chemical name of common salt is

 A) Sodium Chloride B) Potassium Nitrate C) Sodium Nitrate D) Potassium Chloride

Explanation:

The chemical name of common salt is Sodium Chloride with a chemical formula NaCl.

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1 241
Q:

Which equation is an example of a synthesis reaction?

 A) 2H2 + O2 → 2H2O B) Na + Cl → NaCl C) HA + BOH → H2O + BA D) NaCl + AgNO3 → NaNO3 + AgCl

Explanation:

When two or more chemical species combine to form a single product, the reaction is said to be synthesis reaction. It is also called as Direct Combination reaction.

Here in the given options, Sodium (Na) combines with Chlorine (Cl) to form a more complex single product Sodium Chloride (NaCl).