Chemistry Mock Test- 4 - Class 9 MCQ

According to Rutherford’s model of atom, The electrons revolve around the nucleus in well-defined orbits.but it has a drawback:The orbital revolution of the electron is not expected to be stable. Any particle in a circular orbit would undergo acceleration .During acceleration, charged particles would radiate energy. Thus, the revolving electron would lose energy and finally fall into the nucleus. If this were so, the atom should be highly unstable and hence matter would not exist in the form that we know. 

The electronic configuration of the element with atomic number 19 , is 2,8,8,1
The element is potassium. It is an alkali metal with one valence electron. 

In 1806, Proust summarized his observations in what is now called Proust's Law. It stated that chemical compounds are formed of constant and defined ratios of elements, as determined by mass. For example, carbon dioxide is composed of one carbon atom and two oxygen atoms.

Gases can be liquefied by applying pressure and reducing the temperature. When high pressure is applied, and the temperature is lowered, gases can be converted into liquids.

Humidity does not affect the rate of evaporation. The rate of evaporation increases with an increase in surface area, temperature, and wind speed.

The process of conversion of a substance from the liquid state to its vapor state at any temperature below boiling point is called evaporation or vaporization.

The turning of any liquid into vapour is called Evaporation. The factors affecting the evaporation are:

1. Temperature. As the temperature increases, the rate of evaporation also increases.

2. Surface Area. As the Surface area increases, the rate of evaporation increases.

Latent heat of fusion is the amount of heat energy required to change 1 kg of solid into liquid state without any change in temperature, at its melting point.

C is the correct option.a negatively charged ion, i.e. one that would be attracted to the anode in electrolysis.
A. Magnesium (+2)
B. Sulphate (-2)
C. Oxalate (-2)
D. Ammonium(+1)
Hence, only B and C are Anions.

Fog, mist or frost are due to condensation, depending upon the physical conditions of atmosphere.

Increases in heat energy can break attractions between particles and trigger a change of state.

For example, when water freezes water molecules are held in a crystalline structure by hydrogen bonds that form between neighboring water molecules. As heat is added to ice, some of the hydrogen bonds will be broken. This will allow more and more water molecules to move freely and the ice will melt and transition into the liquid state.

Mass percent of solution = (mass of solute / mass of solution)×100%(mass of solute / mass of solution)×100%
=     4    ×100%
   4+36
= 10%.

They have similar chemical properties because isotopes of an element have the same number of electrons as an atom of that element. The electron arrangement is the same owing to same chemical properties. However they have different numbers of neutrons, which affects the mass number. Mass number determines the physical properties such as boiling/melting/density etc

Atomic number of B = Number of Protons = Number of electron in element
= 5
Mass number = Number of protons + Number of neutrons = 5 + 6 = 11
So, symbol of B : 11₅B

A compound is a substance formed when two or more elements are chemically joined. Water, salt, and sugar are examples of compounds. When the elements are joined, the atoms lose their individual properties and have different properties from the elements they are composed of.

N₂ is the chemical symbol for nitrogen gas.

Hund's rule says , when electrons are filled in orbitals of equal energy, one electron enters each orbital until all the orbitals contain one electron with the same spin direction. Then the pairing of electrons take place.

Thus in electronic configuration, the electrons in p subshell are filled in 3 orbitals such that every orbital contains one electron each. The fourth electron will be paired up with the first electron and the other two electrons remain unpaired.

Metal are generally hard and produce tinkling sound when bent. Non-metals are brittle and compounds cannot be bent.

According to his experiment, Rutherford conclusion given below,
Rutherford's first conclusion is that the nucleus is smaller than the atom and second is that inside the atom electrons and nucleus are present. In the atom electrons revolve around the nucleus and rotate itself. The mass of the atom depends on the nucleus. The nucleus only has the maximum mass of the atom. The charge of the nucleus is positive and the charge of electrons is negative.

Only a few particles bounced back because the nucleus is so small / atom is mostly empty space that few collided with a nucleus . If they bounced back it was because of alpha particle and nucleus are positive : repulsion if they bounced back it was because nucleus is massive / dense so alpha particles rebound . "

Hydrogen sulfide is the chemical compound with the chemical formula H₂S. It is a colorless gas with the characteristic foul odor of rotten eggs. It is very poisonous, corrosive, and flammable.

- The atomic number of an element is the number of protons in its nucleus.
- This defines the identity of the element and determines its position in the periodic table.
- Since protons have a positive charge, the atomic number is effectively the electrical charge of the nucleus.
- Electrons, which are negatively charged, balance this charge in a neutral atom.
- Therefore, the atomic number is best described as the electrical charge of the nucleus, making option C correct.

• option ( a)( The no. of atoms in a given compound is fixed ) , is a postulate of dalton atomic theory. 
• Option ( c)  ( Atoms can neither be created nor destroyed) is also, a postulate of dalton atomic theory. 
• Option ( d) ( Atoms cannot be divided) , is also a postulate of dalton atomic theory. 

But option ( b) is not a postulate of dalton atomic theory.
 

1. Most of the space inside the atom is empty because most of the α-particles passed through the gold foil without getting deflected.
2. Very few particles were deflected from their path, indicating that the positive charge of the atom occupies very little space.
3. A very small fraction of α-particles were deflected by very large angles, indicating that all the positive charge and mass of the gold atom were concentrated in a very small volume within the atom.

From the data he also calculated that the radius of the nucleus is about 10⁵ times less than the radius of the atom.

Burning of candle is both physical and chemical change. When the candle burns, the wax slowly melts which freezes after some time (Physical change).Burning of wick is a chemical change as it involves combustion.