Express your answer usingfour significant figures. Use the atomic mass oflithium
ID: 690697 • Letter: E
Question
Express your answer usingfour significant figures.
Use the atomic mass oflithium to calculate the relative abundances of the twoisotopes. Express your answersusing one decimal place. Enter your answers separated by acomma.
lithium-6 abundance,lithium-7 abundance = ??? % , ??? %
Use the atomic mass oflithium to calculate the relative abundances of the twoisotopes. Express your answersusing one decimal place. Enter your answers separated by acomma.
lithium-6 abundance,lithium-7 abundance = ??? % , ??? %
???? ft.
1) A penny has a thickness of approximately 1.0 {rm mm}. If you stacked Avogadro'snumber of pennies one on top of the other on Earth's surface, howfar would the stack extend (in {rm km})? [For comparison, the sunis about 150 million {rm km} from Earth and thenearest star (Proxima Centauri) is about 40 trillion {rm km} fromEarth.] Express your answer usingfour significant figures. 2)Lithium has only twonaturally occurring isotopes. The mass of lithium-6 is6.01512 {rm amu} and the mass oflithium-7 is 7.01601 {rm amu}. Use the atomic mass oflithium to calculate the relative abundances of the twoisotopes. Express your answersusing one decimal place. Enter your answers separated by acomma. lithium-6 abundance,lithium-7 abundance = ??? % , ??? % 3) 1 {rm mol} of sand grains wouldcover the state of Texas to several feet. Estimate how many feet byassuming that the sand grains are roughly cube-shaped, each onewith an edge length of 0.10 {rm mm}. Texas has a land area of268,601 square miles.
Explanation / Answer
1. 6.022x1023 x 1mm =6.022x1023mm 6.022x1023mm x 1m/1000mm = 6.022x1020m 6.022x1020m x 1km/1000m =6.022x1017km 2. 6.941 = (1-x)6.01512 + (x)7.01601 x=0.925 (1-x)=0.075 So there is 92.5% Lithium-7 and 7.5% Lithium6. 3. A = 268m601 mi2 = 695,673km2 is the area of Texas in squared kilometers 0.1mm x 1m/1000mm x 1km/1000m = 1x10-7km is the lengthof each side of the sand grains (1x10-7km)2=1x10-14km2is the area of each sand grain 695,673km2/1x10-14km2=6.95673x1019is how many sand grains it takes to cover the area of Texasonce 6.022x1023/6.95673x1019 = 8656 is how manytimes you can cover the area of Texas with one mole of sandgrains 8656 x 0.1mm x 1m/1000mm = 0.865m is how tall the sand grains willstack on top of each other after covering the area of Texas 8656times. 0.865m x 3.28 feet/1m = 2.84 feet
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