We can be sure that a mole of table sugar and a mole of vitamin C are equal in their a. mass. b. volume. c. number of atoms. d. number of molecules.

Video transcript

Welcome back. The next problem asks which one of the following pairs will contain the same number of molecules A one mole of sodium chloride and 10 g of glucose be one mole of water and one mole of starch c one kg of sucrose and one kg of glucose d one g of sugar and one g of table salt. So let's look at the units and our answers here because we're looking for something that describes a number of molecules. So a mole describes a number in this case six point oh 22 times 10 to the 23rd of items or entities. In this case we would be looking for a number of molecules. The other units here, grams and kilograms are units of mass and they're not really appropriate for comparing numbers of molecules because for instance, if I have here two molecules with very different size. So I've got a tiny little water molecule with just three atoms versus a huge branched policy aka ride chain of starch with thousands of atoms. Well, if I have a gram of water that's going to contain a lot more of these tiny little molecules than a gram of starch in which each molecule is so massive. So understanding that let's look back at our choices, a one mole of sodium chloride and 10 g of glucose. So you're comparing moles entities and grams So we can eliminate choice A As not being a comparison of the number of molecules, choice B says one mole of water and one mole of starch. So in this case a mole of water has six point oh 22 times 10 to the 23rd molecules of water, a mole of starch six point oh 22 times 10 to the 23rd molecules of starch. So Choice be indeed has two things with the same number of molecules. So we can just check back on the other answers to make sure. See one kg of sucrose and a kilogram of glucose. Well, just like in our example, sucrose being a dice aka ride is a larger molecule, then the mono saccharine glucose. So if we're just looking at masses again, that doesn't give us an equal number of molecules. So we can eliminate choice C. And choice D, one g of sugar and one g of table salt. Sugar is a dice aka ride. Sucrose. Table salt is just sodium chloride, so a much smaller molecule so we can eliminate choice D. In the same way. So there we have it. Our correct answer is B. C. You in the next video