A sugar cube is supposed to be equivalent to a teaspoon of sugar. A teaspoon of sugar is about 4.2 g. Table sugar is composed of sucrose, which is a disaccharide of glucose and fructose, with a molar mass of 342.3 g/mol. This means a sugar cube contains (4.2 / 342.3 =) 0.0123 mol of sucrose, or (0.0123 x 6.022 x 10^23 =) 7.39 x 10^21 molecules of sucrose. As one molecule of sucrose contains one molecule of glucose and one molecule of fructose, then there about 7,400 million, million, million molecules of glucose in a sugar cube.
