Complete solutions for all 13 chapters covering Chemistry, Physics and Biology.
Click on any chapter to view detailed solutions
Types of reactions, Balancing equations, Effects of oxidation
pH scale, Neutralisation, Salts
Properties, Reactivity series, Extraction
Covalent bonding, Homologous series, Chemical properties
Nutrition, Respiration, Transportation, Excretion
Nervous system, Hormones, Reflex action
Asexual and Sexual reproduction
Inheritance, Mendel's laws, Sex determination
Mirrors, Lenses, Ray diagrams
Defects of vision, Dispersion, Scattering
Ohm's law, Resistance, Power
Magnetic field, Electromagnet, Fleming's rules
Ecosystem, Ozone depletion, Waste management
This chapter introduces chemical reactions, how to write and balance chemical equations, and different types of chemical reactions.
Magnesium ribbon should be cleaned before burning because:
• Magnesium ribbon has a thin layer of magnesium oxide (MgO) on its surface due to reaction with air.
• This layer prevents the ribbon from burning properly.
• Cleaning with sandpaper removes this oxide layer, exposing fresh magnesium metal for a bright and clean combustion.
We balance the atoms of each element on both sides:
This chapter covers properties of acids and bases, the pH scale, neutralisation reactions, and common salts.
Answer: (d) 10
A solution that turns red litmus blue is basic (alkaline) in nature. Basic solutions have pH greater than 7.
• pH = 1 → Strongly acidic
• pH = 4 → Weakly acidic
• pH = 7 → Neutral
• pH = 10 → Basic ✓
When dilute hydrochloric acid (HCl) is added to zinc granules:
• Zinc reacts with dilute HCl to form zinc chloride and hydrogen gas.
• This is a displacement reaction where zinc displaces hydrogen from the acid.
• Bubbles of hydrogen gas are observed on the surface of zinc granules.
• The reaction is exothermic (releases heat).