To make a mirror for a telescope, you coat the glass with a thin layer of aluminum to reflect the lightIf the mirror has a diameter of 6.0 inches, and you want to have a coating that is 0.015 mm thick, how many grams of aluminum will you need? How many atoms of aluminum are in the coating? The density of aluminum is 2.702 g/cm3The volume of the coating is given by times the square of the mirror radius times the thickness of the coating (because the volume of a cylinder is r2h).
assuming you're coating 1 side of the mirror and the mirror is perfectly flat volume of coating π x (d/2)? x h and using that dimensional analysis you've been so diligently studying mass Al needed 3.14 x (6.0in / 2)? x (2.54cm / 1in)? x 0.015mm x (1cm / 10mm) x 2.702g / cm? 0.74g which you get by entering 3.14 x 3? x 2.54? x 0.015 / 10 x 2.702 into your calculator and round to 2 sig figs and if you notice the units in?.cm?.mmcm.g .- x - x - x - x - grams .1.in?.1.mmcm? as for atoms of Ag you already know gramsall you need is 1 extra sig fig for the intermediate calc 0.739g Ag x (1 mol Ag / 107.9g Ag) x (6.022x10^23atoms Ag / mol Ag) 4.1x10^21 atoms Ag againenter 0.739 / 107.9 x 6.022e23 in your calculator and round to 2 sig figs likewise the units are g .mol.atoms .- x - x - atoms Ag .g.molwhich you can easily see by observing the units canceling out how much of this makes sense?
Yes warm water wash rinse is the recommended method if washing machine has a woollen cycle use that
