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Electrons are negatively charged. Then why are they not attracted towards nucleus and fall into it?

Analyze the diagram given below and identify in which test tube the rate of reaction will be maximum.

Explain the formation of (i) Sodium ion, and (ii) Chloride ion, from their respective atoms giving the number of protons and number of electrons in each one of them. What is the reason for a positive charge on a sodium ion and a negative charge on a chloride ion?

According to Newlands’ Law of Octaves, identify the set of elements that possess similar properties.

Fill in the following blanks with suitable words :

(a) The best evidence that particles of matter are constantly moving comes from the studies of ______and___

(b) The smell of perfume gradually spreads across a room due to ___

(c) Solid, liquid and gas are the three ___of matter.

(d) At room temperature, the forces of attraction between the paricles of solid substances are ___then those wchich exist in the gaseous state.

(e) The arrangement of particles is less orderd in the ___state . However, there is no order in the ___ state.

Identify the conclusions from the Rutherford's alpha ray scattering experiment.

A group of students took an old shoe box and covered it from all sides with black paper. They fixed a source of light (a torch) at one end of the box by making a hole in it and made another hole on the other side to view the light. They placed a milk sample contained in a beaker in between the hole and the torch. They were amazed to see that milk taken in the tumbler was illuminated. They tried the same activity by taking a salt solution but found that light simply passed through it.

Explain why the milk sample was illuminated.Name the phenomenon involved.

pls reply fast

Which of the following is an example of a physical as well as a chemical change?

Which of the following elements will have the largest atomic radii?

A boy is punished and is instructed to run around a circular track on the ground for 1 hour, he loses all his energy in half an hour and falls down. Imagine the boy to be an electron and the ground as an atom. The drawback of which atomic model can you relate to this?

The given equation represents the reaction of sodium metal with water.

Sodium + Water → Sodium hydroxide + Hydrogen

Which of the following chemical equations represents a complete balanced chemical equation for the given word equation?

Give two postulates of the Bohr's atomic model.

Which one on reaction with NaOH solution gives inflammable gas?

What will happen if you keep a solution of copper sulphate in an iron container for a few days? What is the reason for your observation

In Carius method of estimation of halogen, 0.15 g of an organic compound gave 0.12 g of AgBr. The percentage of bromine in the compound is:

In inorganic salt analysis, group sixth cation is _____.

Which property of a substance does the process of distillation use as a basis for separation of components of a mixture ?

Oxides of nitrogen and sulphur form ___ when they react with water vapour present in atmosphere.

(a) What is a mixture? Give two example of mixtures.

(b) What is meant by (i) homogeneous mixtures, and (ii) heterogeneous mixtures? Give two examples of homogeneous mixtures and two of heterogeneous mixtures.

(c) What is the other name of homogeneous mixtures?

A boy is instructed to run around a circular track on the ground for 1 hour. He loses all his energy in half an hour and falls down. Imagine the boy to be an electron and the ground as an atom. The drawback of which atomic model can you relate to this?

Potassium manganate $\left(K_{2}Mn{O}_4\right)$ is formed when:

The following changes represented by letters A, B, C, D can bring about the conversion of iron pyrites (FeS₂) to sulphuric acid (H₂SO₄) in the contact process.

${\mathrm{FeS}}_2\stackrel{A}{\to }{\mathrm{SO}}_2\stackrel{B}{\to }{\mathrm{SO}}_3\stackrel{C}{\to }\mathrm{oleum}\stackrel{D}{\to }{\mathrm{H}}_2{\mathrm{SO}}_4$

(i) Write the balanced equation to show change 'A'.

(ii) Name the above reaction bringing about change 'A'.

(iii) Write the formula of oleum.

(iv) Name the substance C.

(v) What is 'D'? Why is it required?

(vi) State giving reasons, whether 'D' can be used in place of 'C'.

Question 17

Give the chemical formulae for the following compounds and compute the ratio by mass of the combining elements in each one of them.



(a) Ammonia

(b) Carbon monoxide

(c) Hydrogen chloride

(d) Aluminium fluoride

(e) Magnesium sulphide

Which of the following is not a consequence of lanthanide contraction ?

Van Arkel method of purification of metals involves converting the metal to a:

Name the solvent you would use to separate a mixture of sulphur and carbon.

Analyse the options given below and choose an element with the largest atomic radii.