Q.What two monosaccharides are obtained on hydrolysis of sucrose? What is 'invert sugar', and why is it given this name?

On hydrolysis -- by dilute acid or by the enzyme invertase (sucrase) -- sucrose splits into one molecule of glucose and one molecule of fructose, in equal (1:1) amounts.

This resulting 50:50 glucose-fructose mixture is given the special name invert sugar. The name refers to a change in the sign of optical rotation during the reaction: sucrose itself is dextrorotatory (rotates plane-polarised light to the right, $+$), but the product mixture is net levorotatory (rotates it to the left, $-$), because fructose is very strongly levorotatory and this outweighs glucose's more modest dextrorotation. Since the measured rotation flips sign, from positive to negative, over the course of the hydrolysis, the reaction is described as an 'inve …

Recall the two products of sucrose hydrolysis (glucose + fructose, 1:1), then compare the sign of optical rotation before (sucrose, dextrorotatory) and aft …

Assuming 'invert sugar' refers to some structurally inverted form of sucrose -- it is simply the ordinary 1:1 glucose-fructose mixture; 'invert' describes …