Chemistry Answers

A biochemist who is studying the properties of certain sulfur S-containing compounds in the body wonders whether trace amounts of another nonmetallic elements might have similar behavior. To which element should she turn her attention?

(a)F (b)As (c)Se (d)Cr (e)p

Which two of these elements would you expect to show the greatest similarity in chemical and physical properties: B,Ca,He,Mg,P?

Using the spdf notation,write the electron configuration of iodine?

A sample of 0.846 mol Ne gas at 18°C has a volume of 18.5 L under a pressure of 1.09 atm. The gas is then compressed to 10.5 L at 18°C. Calculate the final pressure.

Write the equilibrium‑constant expression for the reaction shown in terms of [A],

 [B],

 [C],

 and [D].

A(g)+B(g)↽−

−⇀

2C(g)+D(g)

Note that 𝐾

c

,

 which is sometimes symbolized as 𝐾

 or 𝐾

eq

,

 denotes that the equilibrium constant is expressed using molar concentrations. For this question, 𝐾

c

 means the same thing as 𝐾

 and 𝐾

eq

.

Calculate the rate constant k from the gradient of the graph, drawn for part (c). All calculations must be shown

Plot a ‘rate against concentration of OH^-‘graph from your results in part (b). Label the vertical and horizontal axes of the graph and include the units. The graph MUST be hand-drawn or plotted by hand.

1-Bromobutane was hydrolysed by an aqueous sodium hydroxide (NaOH) solution. 

     CH₃CH₂CH₂CH₂Br    +   NaOH     →      CH₃CH₂CH₂CH₂OH      +     NaCl 

        1-Bromobutane                                             Butan-1-ol

                       During the reaction, the reactant sodium hydroxide is used up. Samples of the reaction mixture were drawn off at regular time intervals and analysed by titration with standard sulfuric acid to find out the concentration of sodium hydroxide. 

      The results are given in the table below:

 Time / s Concentration of OH-  / mol dm-3

0 0.500

100 0.350

200 0.250

300 0.180

400 0.125

500 0.090

600 0.063

700 0.040

800 0.030

 Select 4 suitable points along your graph [see part (a)] and draw tangents to find the rates. Construct a table of “Rate” against “Concentration” (2 marks). The rates need to be calculated and the calculations shown 

Why is ethanol denser than isopropanol?

We are asked to compare its specific gravity using hydrometer. My readings are 0.820 SG for ethanol and 0.795 SG for isopropanol.

In a 1-L volumetric flask, 20 mL of a 5-M solution was introduced and then filled with water to the mark. What is the new concentration of the diluted solution?