Question

C. MOLECULES IN YOUR NAME Procedure: Use analytical balances and record all your masses to 0.001g. Show all your calculations with correct significant figures and units. 1. Record the mass of a chalk. 2. Write your full name (first, middle and last name) on the blackboard using this chalk. s 3. One the same balance, record the mass of the chalk again. Complete the table below. Grey areas denote calculated values. A Mass before writing (8) B Mass after writing (8) Mass used (g) An c a. Calculate the molar mass of the chalk. (Made of calcium carbonate - Caco) mm Caloze b. How many moles of chalk were in your name? Amars (C) mm Chalk Com o Siswa c. How many formula units of chalk were in your name? molar of Chalk used Avogadros Nis d. What is the % composition of each element in chalk? Va

Answer 1

let A mass before writing 18) B mass after writing to Tomass used (g) y (ny). (a) Molar mass of chalk (CaCO3) = 40 + 12 + 3x16 = 40 +12+48 = 100; . molar mass = 100g/mol (6) moles of chalk in writing name (-y) aven mass 2 mole= - - molar mass (e) No of tormula unit in chalk as used in writing name. no of formula aunt = molex avogadro No. =(x-4) x 61023x102 120 23

(d) Calculation of page composition - Let as I mole of callez - 100 g take any amount of CaCO3, Auswer will be same inespective of amorent taken.) In linole of CaCO3 mass of Ca=40 g mass of c = 12 g mass of 0 = 16x3=488 .: %. age of Ca = 40 x100 %=4079 tage of c = 12 x 100% = 12% page of 0 = 18 x 100%. = 48.4. 100 ase mass of substance 4200) total was