Question

I was wondering if someone could help me with some problems on my test, my teacher allows me to correct them then give them back for 1/2 credit. Along with the correct answer for each id like to know why the answers are wrong and why the new answer is correct. The questiins with a red mark are incorrect.

QUINN A coolant widely used in automobile engines is 38.7 % carbon, 9.7 % hydrogen, and 51.6 % oxygen. Calculate the empirical formula for the compound. a. CaHO3 b. СН.О. с. СНО d. CH O СНO e. 2. What is the total number of atoms contained in 2.00 moles of iron? 118 atoms a. b. 6.02 x 103 atoms 1.20 x 1024 atoms d. 1.2 x 1024 atoms None of the above e. 3. How many atoms are in 0.188 mol Na? a. 3.12 x 10-25 b. 8.84 x 10-24 .13 x 1023 d. 6.02 x 1023 e. 3.20 x 1024 Which of the following 85.0 g samples contain the greatest number of atoms? 4. Tin a. b. Polonium Iron с. d. Zinc e. Lithium 5 How many moles are in 0.802 g of Calcium metal? a. 1.05 mol b. 1.055 mol c. 2.00 mol d.0.0200 mol e. 0.02 mol

Answer 1

1. for the sake of simplicity, assume that you have a total of loog of the compound. Therefore, you have 38.7 g of c, 9.7g of H. and 51.6 g of o. convert each of these to moks; moles of c 38.7 g = 3.225 mol = 12 g/mol moles of H = 9.7g = g. 60 mol 100g/mol moles of o = Sli6g = 3.225 mol 16ooglmol

Here, the c&o mole numbers are same so the ratio of these two elements is 1:1 within the compound. Now, divide the moles of all elements by the smallest among them, which is 3.225 mol This division gives 3.225 molc = 1 mola 3.225 9.60 mol H -3 mol H 3.225 3.225 molo- moto 31225 so, the compound has the empirical frmo сно. so, (d) is correct option. - 1 mol of an element contain 6.0238 1023 atonas So, 2.00 mol of re condain 2.000 6.023x1023 atoms = 1.20x10²t atoms se, (e) is correct option 3. similarly as in D. 188 mol No part 2 (above); contains 0.1888 6. 23 x 1023 atoms = 1.13X1023 atoms 4. The greatest number of atoms comes from the greatest number of moles. mole = E - given mass molar mass The above relation states that for greater number of moles, molar mass should be minimum. Here, Lithium has lowest molar mass out of these so, lithium corresponds to greatest number of atoms. option @ is correct.

mole mass molar mass given mass = 0.802 g And molar mass of Ca = 40.078 g/mol moks of Car 0.802 g -0.02 40.078 gimo so, obtion (e is correct. mol