Chemistry MCQs for NEET — Practice Questions with Answers

The specific rotation of an aqueous solution of sucrose before hydrolysis is ext{+66.5}^ ext{°}. Specific rotation is a characteristic property of a chiral substance and is used to identify specific substances and concentrations.

The phenomenon when the rotation of sucrose solution is reversed is known as 'inversion'. Inversion occurs when sucrose, which is dextrorotatory, hydrolyzes into glucose and fructose, which results in a mixture that is levorotatory. This change in the direction of optical rotation from right to left is called inversion.

Before hydrolysis, sucrose is dextrorotatory, which means it rotates the plane of polarized light to the right. After hydrolysis, the products are glucose and fructose, which result in a levorotatory mixture because fructose has a stronger levorotatory effect compared to the dextrorotatory effect of glucose. Therefore, the optical rotation changes from dextrorotatory to levorotatory.

Sucrose is commonly chosen as the standard for sweetness of sugars. In sweetness comparison, sucrose is assigned a value of 1 (or 100 in some scales), and the sweetness of other sugars is compared relative to sucrose.

When sucrose is heated at 486 K (approximately 213°C), it undergoes a decomposition reaction and forms caramel. This process is known as caramelization, a non-enzymatic browning reaction that produces various compounds responsible for the characteristic color and flavor of caramel.

In maltose, the two glucose units are linked by an α(1→4) glycosidic bond. This means that the first carbon (C1) of one glucose molecule is linked to the fourth carbon (C4) of the second glucose molecule through an oxygen atom. Therefore, the correct option is $ C_1 - O - C_4 $.

The sweetness index of various sugars is a measure of their relative sweetness compared to sucrose (which has a sweetness index of 100). For fructose, the sweetness index is approximately 173, for glucose it is about 74, and for lactose, it is around 16. Thus, the correct option is 173, 74, 16.

Before alcohol can be obtained from starch, the starch must first be broken down into simpler sugars. This process involves the conversion of starch into maltose by the action of the enzyme amylase. Maltose is then further broken down into glucose, which is subsequently fermented to produce alcohol. Therefore, the correct answer is maltose.

Maltose is a disaccharide composed of two glucose molecules. When maltose undergoes hydrolysis, it breaks down into two glucose molecules. Therefore, the correct answer is maltose.