General Chemistry Answers

A 30.0 L tank contains 2.5 kg of neon gas with a pressure of 98.0 atm at 27°C. How many kilograms of O2 can fill the tank under the same pressure and temperature?

4. Phosphorus oxychloride, POCl3, is a type of industrial raw material. It is a colourless and

transparent liquid, and it has an unpleasant irritating odour. It will smoke intensely in

humid air.

(a) Draw all the possible Lewis structures for POCl3. [2 marks]

(b) Determine the most plausible structure from 4 (a). Explain your answer.

[4 marks]

(c) Predict, explain and label the molecular geometry and the bond angles of the structure

in 4(b) [4 marks]

(d) Deduce the polarity of the structure in 4(b). [6 marks]

Why moles of sulfate (SO4^2-) in BaSO4 are equal to moles of BaSO4?

The sulfate in unknown solid can be precipitated by adding

Calculate AH for the reaction: CHa (g) + H2 (g) ›CHa (g), from the following

data.

CHA (g) + 3 02 (g) ->2 CO2 (g) + 2 H20 (1)

AH=-1411. kJ

CHa (g) + 3½ Oz (g) ->2 COz (g) + 3 H20 (1)

AH=-1560, kJ

H2 (g) + ½ 02 (g) > H20 (1)

AH=-285.8 kJ

the following data is given:

t = 10,   20,    30,    40     

R= 30,  15,   7.5,  3.75

Which of the following numbers best describes the halving time (half-life)? (To answer the question you may draw a semi-log plot, i.e., plot logR

log⁡R against t, but may also be able to guess it by looking at the data.)

a) 5

b) 20

c) -10

d) 10

The half-life of Cesium-137 is 30 years. Suppose the intial radioactivity of a sample is 170-Bq.

i. What is the radioactivity after 8 years? (give the answer with accurancy of 2 decimal places)

ii. After how long will the radioactivity be 18 Bq? (give the answer as number of years with accurancy of 1 decimal place )

A weak acid has a pK value of 3.8. A solution contains 0.1 M of the acid and 0.3 M of the negatively charged ion.

What is the pH of the solution? Express the result to two decimal places.

pH =    

from the elements carbon oxygen neon sodium magnesium aluminium sulphur chlorine and argon which cannot give out compound

What mass of chromium metal is in a sample that contains 6.9 × 1025 formula units of ammonium dichromate, (NH4)2Cr2O7(s)?