Jan 282014
 


Different reactions take place with different rates. The branch of physical chemistry that deals with the study of rate of chemical reaction is called chemical kinetics.
During chemical reaction, concentration of reactants decreases while that of product increases. Thus, the rate of reaction may be defined as the decrease in the concentration of reactant or the increase in the concentration of product per unit time.

Let us consider a reaction,
A → B
When time (t) = t1, (A)1 → (B)1
When time (t) = t2, (A)2 → (B)2
If t2 > t1,
Rate of reaction = – (A)2 – (A)1/t2 – t1 = +(B)2 – (B)1/t2 – t1

Here, the negative sign indicates that the concentration of reactants decreases with time. The rate of reaction is measured in molL-1sec-1.

Factors affecting rate of reaction

There are many factors affecting the rate of reaction. Some of them are described below:
i) Size of particle: Rate of chemical reaction increases with the increase in the surface area or decrease in size of reactant particles. For example, when calcium carbonate is reacted with dilute hydrochloric acid, calcium chloride and water are formed with liberation of carbondioxide gas as:

CaCO3 + 2HCl → CaCl2 + H2O + CO2

Rate of reaction can be monitored by the evolution of carbondioxide gas. Evolution of carbondioxide gas is more, when powdered CaCO3 is used rather than lump of CaCO3.

ii) Concentration: Rate of chemical reaction is directly proportional to concentration of the reactants. When concentration is increased, the frequency of collisions between reactant molecules increases. This increases the rate of reaction. In the above given reaction, the evolution of carbondioxide is more rapid when concentrated hydrochloric acid is used rather than dilute hydrochloric acid.

iii) Temperature: The rate of reaction also depends upon temperature. Rate of reaction increases with the increase in the temperature. When temperature is increased, the kinetic energy of reactant molecules increases and their collisions become more effective. It has been found that the rate of reaction increases by two to three times upon each 10oC rise in temperature.

iv) Catalyst: Catalyst increases the rate of reaction by providing alternate path for the reaction having lower activation energy. For example, iron acts as a catalyst during the manufacture of ammonia by Haber’s process. Similarly, the decomposition of potassium chlorate is catalysed by using manganese dioxide.

Average and Instantaneous Rate

Concentration of reactants decreases with time and hence rate of chemical reaction decreases with the propagation of reaction. The rate of reaction at certain interval of time is called average rate of reaction.
To determine average rate, a graph between concentration of reactant or product is plotted against time and concentrations at given time intervals are noted and average rate is determined.

Let us consider a reaction,

A → B

graph 12Average rate = – (A)2 – (A)1/t2 – t1 = + (B)2 – (B)1/t2 – t1
or, Average rate = –Δ(A)/Δt = +Δ(B)/Δt

Similarly, the rate of chemical reaction at a particular instant of time is called instantaneous rate of reaction. To determine the instantaneous rate, a graph between concentration of reactant or product is plotted against time. Then a perpendicular is drawn from the curve to the instant of time where the rate is to be determined. Finally, the slope of the tangent at the corresponding point on the curve gives the instantaneous rate.

34

Instantaneous rate = – (A)2 – (A)1/t2 – t1 = + (B)2 – (B)1/t2 – t1
or, Instantaneous rate = –dA/dt = +dB/dt
The average rate becomes instantaneous rate of reaction when Δt → 0.
∴ Instantaneous rate = Δt lim→ 0 Average rate
or, Instantaneous rate = Δt lim→ 0 – Δ A/Δ B
or, Instantaneous rate = –dA/dB

Jan 282014
 

SLC Model Question Set 2 (Accountancy)

Group ‘A’
Answer the following questions in one sentence. 5×1=5

1. Write the full form of GATT.
2. What is Bank overdraft?
3. What is Final Account?
4. Who is the final auditor of Private business organization?
5. Write the AGF no. of Statement of revenue & Statement of security deposit.

Group ‘B’
Give short answer of the following questions. 8×5=40

6. Define resolution. Explain it types.
7. What is alphabetical filing system? Mention four advantages and disadvantages of it.
8. What is invoice? Describe its three types.
9. From the following particulars, prepare Trial Balance of DES.

Capital    500,000.00 Reserve Fund    230,000.00
Purchase    525,000.00 Drawing      40,000.00
Depreciation      15,000.00 Bank overdraft    350,000.00
Creditor      65,000.00 Account payable      75,000.00
Inventory    100,000.00 Loose & tools    540,000.00


10. From the following particular, prepare Profit and Loss Account of SHA for the year 2069/70.

Groff Profit    100,000.00 Commission      25,000.00
Bad Debt      38,000.00 Corporate tax        5,000.00
Discount        7,000.00 Discount received      15,000.00
Interest charge      11,000.00 Interest from investment      30,000.00
Legal charge      20,000.00 Advertisement      15,000.00
Rent      18,000.00 Interest on capital      15,000.00


11. Prepare Balance Sheet of GFS, Bhaktapur for fiscal Years 2069/70.

Capital    300,000.00 Income due    120,000.00
Net profit    450,000.00 Drawing      90,000.00
Vehicle    200,000.00 Furniture      30,000.00
Building    310,000.00 Closing inventory    100,000.00
Debtors      80,000.00 Bank overdraft    200,000.00
Outstanding salary      50,000.00 Investment      70,000.00


12. What is new accounting system ? Explain its four features.
13. ‘Bank cash book is also known as multi-ledger column’. Explain it.

Group ‘C’
Write the long answer to the following questions. 10×3=30

14. What is Central Bank? Explain its eight functions.
15. Prepare journal voucher for the following transactions provided by District Education Office, Bhaktapur.

a. On 2069-11-01 Received a bank order of Rs. 300,000 and budget
released of Rs. 350,000
b. On 2069-11-02 Cheque no. 0012, issued to accountant
Mr. Sharma in advance for purchase of ten chairs Rs. 2000 per chair.
c. On 2069-11-03 Purchased two computer for Rs. 20,000 each and
issued a cheque for the payment.
d. On 2069-11-04 A cheque of Rs. 5,000 is issued to office assistance
Mr. Ganesh for the establishment of Petty Cash Fund.
e. On 2069-11-20 Issused a cheque of Rs. 200,000 for the salary of
Falgun after deduction of Provident Fund Rs. 20,000 and
income tax Rs. 5,000.


16. Prepare the statement of expenditure of the month of Ashoj 2069.

BH. No. Budget Head  Annual budget  Expenditure up to Bhadra  Expenditure of Ashoj
21111 Salary    600,000.00    100,000.00    50,000.00
22311 Office Expense      75,000.00      15,000.00      3,000.00
21121 Uniform      34,000.00      10,000.00      2,000.00
22711 Miscellaneous      18,000.00        3,000.00      1,500.00
29411 Vehicles    120,000.00      20,000.00    10,000.00
29311 Furniture      40,000.00      16,000.00      7,500.00
   887,000.00    164,000.00    74,000.00


Additional information:
a) Total revolving found released Rs. 300,000.
b) Unclear advance of furniture Rs. 10,000.
c) Petty cash fund Rs. 3,000.



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