18 and 19 ??

Volume of O2 (g) effuses in 1.000 s from a When the same device is used under the same conditions, effusion rate of an unknown gas is 15.0 mL/s. Calculate the density of this unknown gas. (10) A) 1.51 g/L B) 2.55 g/L C) 0.66 g/L D) 0.39 g/L E) 0.21 g/L 16) Calculate the change in internal energy (AU) when 2 moles of CO are converted to 2 moles of CO2 at 1 atm and 25C. 2 CO(g) + O2(g) 2 CO2(g) AH=- 566.0 kJ/mol A) -568,5 kJ/mol B) 563,5 kJ/mol C) -1912,8 kJ/mol D) -1915,7 kJ/mol E) -566 kJ/mol E) None 17) Which one of the followings is a weak acid? ) B) HBr C) HF D) HI 18) According to VSEPR theory, which of the following has the largest bond angle? (H 6C A) HCN B) SF2 C) BF3 D) HOS 19) Calculate the pH of the 0.10 M CHCOOH solution (for acetic acid Ka=1.8 x 105) A) 1.0 B) 2.9 C) 4.7 D) 5.7 EN 16S ISP) 9F sB E) PF: E) None F: H 20) Which of the following statements is wrong according to the reaction ? F: H :I-B + IN-H - 1-B-N-H OF: :F A) BF is a Lewis acid B) BF; takes electron pair C) According to Arrhenius, this is a neutralization reaction D) Electron pair on the nitrogen is used in the formation of chemical bonding E) None 8 from the