Lab Exam Time Allowed: 1 hr CHM 201-003 Answer the questions in order in the exa

Question

Lab Exam Time Allowed: 1 hr CHM 201-003 Answer the questions in order in the exam book. H, 1.0, 0 16.0; C12.0; K 39.1, Cu 63.5, s 320 amu. I. A compound copper and sulfur only was found to contain 79.8 % copper, what is the empirical formula of the compound? 2. Balance the equation below then calculate how many grams of carbon dioxide can be obtained by burning 4.00 g of CHa with 4.00 g of oxygen: CH4(g) + O2(g) CO2(g) + H2O(/) 3. Balance each of the following equations: a) Caco,(s) + HCl(aq) CaCl2(oq) + CO2(g) + H20(1) b) Baclloq) + Na,SOdoq) Baso,(s) + NaCl(aq) c) Al(OH)3(s) + HNOs(aq) Al(NO3)3(aq) + H2O(/) d) Fes(s) + HCl(aq) FeCl2(aq) + H2S(1) 4. Write a net balanced ionic equation for each of the reactions in Q3 above. 5. A 0.5035 g of potassium hydrogen phthalate (HCsH.O.K, a weak monoprotic acid) required 22.55 mlL of a NaOH solution for titration to a phenolphthalein endpoint. What is the molarity of the NaOH solution? 6. Use the data below to calculate the enthalpy of formation,ap of Mg0: Mg(s)019) MgO(s): :-82.6 k/mol Mg0(s) + 2 HCI(aq) MgCl2(aq) + H2O(/) Mg(s) + 2 HCI(aq) MgCl2(aq) + H2(g) H2(g) + ½ O2(g) H20(n -388.3 kJ/mol

Explanation / Answer

Q1

assume 100 g of copmounds

79.8 g of copper, (100-79.8 ) = 20.2 g ofSulfuer

mol of Copper = mass/MW = 79.8/63.5= 1.25

mol of S = mass/MW = 20.2/32 = 0.63

ratio = 1.25/0.63 =2

then, 2 mol of Copper per mol of S

Cu2S

Q2

balance

CH4(g) + O2(g) = CO2(g) + H2O(l)

balance C

CH4(g) + O2(g) = CO2(g) + H2O(l)

balance H

CH4(g) + O2(g) = CO2(g) + 2H2O(l)

balance O

CH4(g) + 2O2(g) = CO2(g) + 2H2O(l)

this is now balanced

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