While diluting an acid, why is it recomm | Class 10 Science Chapter Acids, Bases and Salts, Acids, Bases and Salts NCERT Solutions

When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Find the value of the resistance of the resistor.

Outline a project which aims to find the dominant coat colour in dogs.

Draw the structure for the following compounds.                

       (i)    Ethanoic acid             (ii)   Bromopentane*
       (iii)  Butanone                   (iv)   Hexanal.

*Are structural isomers possible for bromopentane?

A hot plate of an electric oven connected to a 220 V line has two resistance coils A and B, each of 24 Ω resistance, which may be used separately, in series, or in parallel. What are the currents in the three cases?

How is the sex of the child determined in human beings?

(a)  What property do all elements in the same column of the Periodic Table as boron have in common?
(b)  What property do all elements in the same column of the Periodic Table as fluorine have in common?

Calculate the number of electrons constituting one coulomb of charge.

A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits – blood group A or O – is dominant? Why or why not?

What is an homologous series? Explain with an example.

Why is variation beneficial to the species but not necessarily for the individual?

Which one of the following materials cannot be used to make a lens?

(a) Water        (b) Glass        (c) Plastic        (d) Clay

 Balance the following chemical equations.

(a) HNO₃ + Ca(OH)₂ → Ca(NO₃)₂ + H₂O
(b) NaOH + H₂SO₄ → Na₂SO₄ + H₂O
(c) NaCl + AgNO₃ → AgCl + NaNO₃
(d) BaCl₂ + H₂SO₄ → BaSO₄ + HCl

Which of the following statements is not a correct statement about the trends when going from left to right across the periods of periodic Table.

(a) The elements become less metallic in nature.
(b) The number of valence electrons increases.
(c) The atoms lose their electrons more easily.
(d) The oxides become more acidic.

Why are carbon and its compounds used as fuels for most applications?

The kidneys in human beings are a part of the system for

   (a) nutrition.                  (c) excretion.
   (b) respiration.              (d) transportation.

Which of the following terms does not represent electrical power in a circuit?

(a) I²R          (b) IR²          (c) VI          (d) V²/R

What kind of mirror – concave, convex or plain – would be best suited for use in a solar cooker? Why?

What were the criteria used by Mendeléev in creating his Periodic Table?

Give any two ways in which non-biodegradable substances would affect the environment.

Name the substance which on treatment with chlorine yields bleaching powder.