Unit cell dimensions for polyethylene may be assumed to be as follows: a-0.741 nm, b=0.496 nm, c=0.254 nm, a=ß=y= 90° the wavelength of cuk radiation is 0.1542 nm. 17.1 a flat-plate x-ray diffraction pattern was obtained from an unoriented sample of polyethyl- ene using cukk, radiation. it consisted of three rings of radius 22.2, 36.6 and 19.7 mm. the specimen-to-film distance was 50 mm. calculate the d-spacing of the planes giving rise to these reflections. it is thought that these reflections are from (hk0) type planes. draw a scale diagram of the unit cell of polyethylene projected along the c-axis. measure the spacing of the low-index (hk0) type planes and hence identify the planes giving rise to the observed reflections

Abeam of electrons with of wavelength of 7.5 x 10-6 m is incident on a pair of narrow rectangular slits separated by 0.75 mm. the resulting interference pattern is projected onto a screen 10.0 m from the slits. what is the separation of the interference maxima in the resulting interference pattern?

Hydrogen and helium are both members of?

Fill in the blanks with the numbers is a measure of the resistance to flow. a high liquid has a high resistance to flow and flows slowly. the ancients thought everything in the world was made of 4 we now know that there are 94 naturally occurring and scientists have created another 24 i am certain they will create even more. honey flows slowly because it has a high to flowing. a can be separated by physical means because it contains more than one pure substance and 2 pure substances are not chemically bonded to each other. a cannot be separated by physical means. all matter is made up of all elements are with the same number of protons. if it is just a single or many bonded together, if all of them have the same number of protons, it is an element. in a piece of pure iron metal, all the are joined together, that piece of iron metal is called elemental iron. a single of iron is called elemental iron. a mixture has differences from place to place. we might need a microscope to see them or they might be obvious to the unaided eye. there are surfaces separating it into different phases. a mixture is the same everywhere. it is uniform. there are no surfaces separating it into different phases. if different kinds of atoms (different elements) are bonded together by their electrons, it is called a there are physical means of to isolate the different pure substances in a mixture and there are chemical means of to isolate the different elements in a compound. 1. element 2. compound 3. mixture 4. heterogeneous 5. homogeneous 6. pure substance 7. atoms 8. separation 9. viscosity 10. resistance