Identify the following statement as true or false and choose the correct explana

Question

Identify the following statement as true or false and choose the correct explanation. "For solutions same molarity at the same temperature, the pressure needed for reverse osmosis of a sodium chloride solution will always be less than the pressure needed for a calcium chloride solution" a. True, because the van 't Hoff factor is smaller for sodium chloride. b. False, because the van 't Hoff factor is smaller for sodium chloride. c. True, because the molar mass of sodium chloride is smaller. d. True, because the van 't Hoff factor is larger for sodium chloride. e. False, because the van 't Hoff factor is larger for sodium chloride. Balance the following redox reaction under basic aqueous condition using the smallest whole-number coefficients possible. On which side does OH^- appear, and what is its coefficients? Cr(OH)_2(s) + CIO_3^- (aq) rightarrow CrO^2-_4 (g) + Cl^- (aq) a. left, 1 b. right, 2 c. right, 3 d. left, 4 e. OH^- is not required to balance the equation The normal boiling point of benzene is 80.1 degree C, and its enthalpy of vaporization is 30.76 KJ/mol. What is the approximate vapor pressure of benzene at 30.0 degree C? a. 0.177 atm b. 0.926 atm c. 0.998 atm d. 5.65 atm e. 0.839 atm What is the formula of the precipitate that forms when aqueous Fe(NO_3)_3 and aqueous Na_2CO_3 are mixed? a. Na_2 (NO_2)_3 b. FeCO_2 c.Na_2Fe d. CO_2 NO_3 e. Fe_2(CO_3)_3 Indicate which of the following molecule exhibits the greatest dispersion forces. a. CH_4 b. C_2 H_2 c. CH_2 CH_2 CH_2 CH_3 d. CH_3CH_2CH_3 e. CH_2CH_3 In which of the following does manganese have the highest oxidation number? a. MnO_2 b. K_2MnO_4 c. Ba(MnO_4)_2 d. Mn(NO_3)_2 e. MnF_3

Explanation / Answer

Q25

NaCl = 2 ions, Na+ and Cl-

CaCl2 = Ca+2 and 2Cl- then

the Posmotic = i*M*RT

where i = number of ions (vant hoff effect)

therefore, Posmotic for CaCl2 > Posmotic NaCl

i NaCl > i CaCl2

The statement is in general true, so ginore all "false" answers

it is true because vant hoff factor is smaller for sodium chloride

choose A

Q26

balance this

first step, split in half cells

Cr(OH)3 --> CrO4-2

ClO3- --> Cl-

balance O

H2O + Cr(OH)3 --> CrO4-2

ClO3- --> Cl- + 3H2O

balance H

H2O + Cr(OH)3 --> CrO4-2 + 5H+

6H+ + ClO3- --> Cl- + 3H2O

balance charges

H2O + Cr(OH)3 --> CrO4-2 + 5H+ +3e-

6e- + 6H+ + ClO3- --> Cl- + 3H2O

balance e-

2H2O + 2Cr(OH)3 --> 2CrO4-2 + 10H+ +6e-

6e- + 6H+ + ClO3- --> Cl- + 3H2O

add all

6e- + 6H+ + ClO3- + 2H2O + 2Cr(OH)3 --> 2CrO4-2 + 10H+ +6e- +  Cl- + 3H2O

cancel common terms

ClO3- + 2Cr(OH)3 --> 2CrO4-2 +4H+ +  Cl- + H2O

add OH-

4OH- + ClO3- + 2Cr(OH)3 --> 2CrO4-2 +4H2O +  Cl- + H2O

4OH- + ClO3- + 2Cr(OH)3 --> 2CrO4-2 +5H2O +  Cl-

then..

OH- appears in the left side, with 4 coefficient

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