Question 6 A test tube has a colorless aqueous layer of NaI solution and an colo

Question

Question 6

A test tube has a colorless aqueous layer of NaI solution and an colorless organic layer of methylene chloride. When a few mL of colorless chlorine water is added to this test tube. The organic layer became pink. What is causing this pink color in the organic layer?

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Question 9

A water sample with unknown mass absorbed 100.0 J of heat and the temperature increased from 25.0 C to 29.8 C. What is the mass of this water sample? Specific heat of water = 4.184 J/(gC).

Note: To avoid any sig fig issues, please keep only two sig figs for your input!!

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Question 10

Which one is correct about the following process?

CH4 + 2 O2 --> CO2 + 2 H2O

Question 11

100.0 mL of 1.00 mol/L NaOH reacted with 65.4 mL of 1.00 mol/L CH3COOH solution and the temperature increased from 20 to 22 C. How many moles of NaOH get and CH3COOH are neutralized?

Note: to avoid any sig fig issues, please use regular decimal instead of scientific notation and keep 3 sig figs for your input!!

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Question 12

At room temperature, H2SO4 is dissolved in water and the solution is much hotter. So the dissolution of H2SO4

Explanation / Answer

Answer – Q 6) When a few mL of colorless chlorine water is added to this test tube then there is reaction between Cl2 and NaI and formation of NaCl in aqueous layer and I2 in organic layer and we know when I2 is soluble in the aqueous layer it is formed brown solution and when it is in the organic layer formed faint pink color, so pink color in the organic layer due to formation of free iodine.

So answer is I2

Q 9) Given, heat, q = 100 J, specific heat of water, C = 4.184J/goC. ti =25.0, tf = 29.8oC

We know formula

q = m*C*t

100 J = m * 4.184J/goC * (29.8-25.0)oC

100 J = 20.08 J.g-1 * m

m = 100 J /20.08 J.g-1

     = 5.0 g

So mass of water is 5.0 g

Q 10) Given, reaction CH4 + 2 O2 -----> CO2 + 2 H2O

This is the combustion reaction and we know all combustion reaction are the exothermic reaction. Exothermic reaction means releasing the heat, so the enthalpy change is negative

So the answer is - It is exothermic with negative enthalpy change.

Q 11) Given, 100.0 mL of 1.00 mol/L NaOH

65.4 mL of 1.00 mol/L CH3COOH

We need to calculate the moles of each

Moles of NaOH = 1.0 M * 0.100 L

                         = 0.100 moles

Moles of CH3COOH = 1.0 M * 0.0654 L

                                  = 0.0654 moles

We know the reaction

NaOH + CH3COOH ---> CH3COONa + H2O

So mole ration is 1:1 and we have lowest moles of CH3COOH, so limiting reactant is CH3COOH

And moles of used for both NaOH and CH3COOH are 0.100 moles respectively.

Q 12) When H2SO4 is dissolved in water and the solution is much hotter, means there is heat evolved when H2SO4 is dissolved in water. So the dissolving the H2SO4 in water is exothermic reaction, so answer is - released some heat and has a negative enthalpy change

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