Part-I Secondary and Senior Secondary Standard: MCQ — 350 Practice Questions with Answers

Explanation

Le Chatelier's principle predicts that lowering temperature favours the exothermic direction, here formation of SO3. Increasing pressure favours the side with fewer gas molecules; the forward side has 2 mol gas compared with 3 mol gas on the reactant side. Therefore low temperature and high pressure give the greater equilibrium yield, apart from kinetic-rate considerations.

Explanation

The empirical formula gives the simplest whole-number atom ratio. For CH2O, the empirical formula mass is 12 + 2 + 16 = 30 g mol^-1. The multiplier is molecular mass divided by empirical formula mass, 180/30 = 6. Multiplying all subscripts by 6 gives the molecular formula C6H12O6.

Explanation

Down syndrome is a chromosomal disorder caused most often by the presence of an additional chromosome 21. That is why it is also called trisomy 21 in standard genetics teaching.

Explanation

Among algae, hard matching questions often mix pigment and reserve food across classes. Rhodophyceae are red algae because phycoerythrin predominates, and their reserve food is floridean starch. Brown algae instead have fucoxanthin and store laminarin or mannitol, while green algae store starch.

Explanation

Fine particles and molecules in the atmosphere scatter shorter wavelengths of visible light more effectively than longer wavelengths. Since blue light has a shorter wavelength than red light, scattered blue light reaches our eyes from different directions, giving the clear sky its blue colour.