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In modern periodic table nitrogen is placed just before oxygen in the 2nd period because:

Salts are formed when:

How is ph scale calculated

The equations given below relate to the manufacture of sodium carbonate (molecular weight of Na₂CO₃ = 106).

Questions based on the production of 21.2 g of sodium carbonate.

What mass of sodium hydrogen carbonate must be heated to give 21.2 g of sodium carbonate (Molecular weight of NaHC0₃ = 84)?

Which of the following salts produces most basic solution?

Can metals-metals have a covalent bond

Discuss briefly the physical and chemical properties of ethanoic acid.

Did Dobereiners triads also exist in the columns of Newland's Octaves ? Compare and find out.

Write the balanced chemical equation for the following reaction.

Lead nitrate solution is added to sodium chloride solution.

The following reaction is an example of a
$2Pb\left(N{O}_3{)}_2\right(s\left)\stackrel{Heat}{\to }2PbO\right(s)+4N{O}_2(g)+O_2(g)$
I. Combination reaction
II. Decomposition reaction
III. Endothermic reaction
IV. Exothermic reaction

(a) State one appropriate observation for: Electricity is passed through molten lead bromide.

(b) State which of these will act as a non-electrolyte

(i) Liquid carbon tetrachloride

(ii) Acetic acid

(iii) Sodium hydroxide aqueous solution

(iv) Potassium chloride aqueous solution

(c) Copper sulphate soln. is electrolysed using copper electrodes.

(i) Which electrode to your left or right is known as the oxidising electrode and why ?

(ii) Write the equation representing the reaction that occurs.

(iii) State two appropriate observations for the above electrolysis reaction.

(d) Identify : A gas which does not conduct electricity in the liquid state but conducts electricity when dissolved in water.

Why are large alkane molecules cracked to form samller molecules to use it as a fuel?

Name the compounds formed when methane burns in :
(a) sufficient air,
(b) insufficient air.
Give a balanced equation.

Explain why:
(a) Covalent compounds have generally low melting points.
(b) Ionic compounds have generally high melting points.

1. 14

What is the definition of acidic salts?

Greenish layer appears on the copper utensils if they are not cleaned for few days. Give reason.

Which kind of chemical reaction takes place when electric current is passed through fused lead Bromide?

Which of the following are the properties of Graphene?

The skin has and needs natural oils. Why is it advisable to wear gloves while working with strong alkalis ?

Calcination is a process in which the ore is heated strongly in the absence of air to remove volatile impurities. It thermally decomposes the carbonate.
$2F{e}_2{O}_3.3H_{2}O\stackrel{Calcination}{\to }A+3H_{2}O$
Find out $A$:

Which of the following factors influence the rate of chemical reactions?

Is NH4Cl soluble in NaOH

The element whose electronic configuration is $1s^2,2s^2,2p^6,3s^2$ is a/an?

What will be the order of $I^{st}$ ionisation energy?

Which the following is not a property of metals?

The atomic weight of Al is 27. When a current of 5 Faradays is passed through a solution of Al⁺³ions, the weight of Al deposited is

Is dry hcl acid?

When iron (Fe) is exposed to moist atmosphere for a long time, rust is formed which is a layer of a brown flaky substance. What is the chemical composition of this iron rust?

What is the catalyst used in the catalytic oxidation of ammonia?

Generally the ionization enthalpy in a period increases but there are some exceptions, the one which is not an exception is?

What is ore enrichment? Is it different for different for different types of ores?

Although there are several ores, 80% of the world copper production comes from the ore chalcopyrite ($CuFe{S}_2$). The extraction of copper from chalcopyrite involves partial roasting, removal of iron and self-reduction. In the self-reduction step, the reducing species is:

What happens when hydrogen chloride gas is exposed to air?

Write the name and structure of a saturated compound in which the carbon atoms are arranged in a ring. Give the number of single bonds present in this compound.

How many vertical columns are there in the modern periodic table and what are they called?

Calculate the pressure of one mole of nitrogen gas in a 10 L cylinder at ${50}^{\circ }C$ using the Van der Waal's equation.Also find the value of ideal gas pressure.(Van der Waal's constants a and b for nitrogen are $1.4L^{2}atmmo{l}^{-2}and0.04L^{2}mo{l}^{-1}$ respectively) .

The mass of 10 moles of ${\text{H}}_2\text{O}$ is

Which of the following statement is correct?

Olfactory indicators with examples and their changes when react with acid or base

Two organic compounds X and Y contain Carbon and Hydrogen only and have vapour densities 13 and 39 respectively. State the molecular formula of X and Y.