As you have asked about the important topics for the SRM University Engineering Entrance Exam (SRMEEE), I am giving you information about it, check bellow for the details
Physics

Units and Measurement
Mechanics
Gravitation, Mechanics of Solids and Fluids
Oscillations and Wave Motion
Heat and Thermodynamics
Ray and Wave Optics and Magnetism
Electricity and Magnetism
Atomic Physics and Relativity
Dual Nature of Matter and Nuclear Physics
Electronics and Communication

Chemistry

Some Basic Concepts in Chemistry
The States of Matter
Chemical Families–Periodic Properties
Atomic Structure
Chemical Bonding and Molecular Structure
Chemical Energetic
Chemical Thermodynamics
Solutions
Chemical Equilibrium
Electro-chemistry
Surface Chemistry, Chemical Kinetics and Catalysis
Purification and Characterization of Organic Compounds
Some Basic Principles of Organic Chemistry
Hydrocarbons
Organic Compounds Containing Oxygen
Organic Compounds Containing Nitrogen
Polymers
Bio-Molecules
Chemistry in Everyday Life

Mathematics

Sets, Relations and Functions
Complex Numbers
Matrices and Determinants
Applications of Matrices and Determinants
Quadratic Equations
Permutations and Combinations
Mathematical Induction and its Applications
Binomial theorem and its Applications
Sequences and Series
Differential Calculus
Applications of Differential Calculus
Integral Calculus
Differential Equations
Straight Lines in Two Dimensions
Circles in Two Dimensions
Conic Sections in Two Dimensions
Vector Algebra
Measures of Central Tendency and Dispersion
Probability
Trigonometry