HS 1st Year Unit Test Cemistry Question Paper
1st unit important modal questin paper
Class : HS 1st year
Sub : Chemistry
1. Answers any ten :
(i) Define one mole of a substance ?
(ii) State modern periodic law ?
(iii) How many groups and periods present in a modern periodic table ?
(iv) In which period and group an element having atomic number 16 belongs ?
(v) State pauli’s exclusion Principle ?
(vi) How many orbitals present in an orbit having n = 3 ?
(vii) Calculate the Volume occupied by 22g of CO2 at N.T.P
(viii) State Heisenberg uncertaity Principle ?
(ix) Define orbital ?
(x) Define morarily of a solution ?
(xi) Define atomic number of an element ?
(xii) What is the cause of periodicity in propertics ?
(xiii) Why element belonging to the same group have similar properties ?
2. Answer the following questions
A) How many significant figures are present in the followings .
i) 208
ii) 0.00035
iii) 126000
iv) 500.0
B) Express the following scientific notation.
i) 0.00058
ii) 267000
iii) 8008
iv) 6.0012
C) Round off to three significant figures.
i) 35.516
ii) 11.4307
D) From avagadro’s hypothesis, prove that the molecular mass of any gas is twice of its vapour density .
E) Explain why molarity of a solution decrease with rise of temperature but molality remains constant.
3. Answers the following question
a) States of the postulates of bohr’s atomic theory of hydrogen atom .
b) Using S,P,d and f notations, describe the orbitals with the following quantum numbers.
i) n=1, l=0
ii) n=4, l=1
iii) n=4 , l=3
iv) n=3, l=2
c) why 2d orbitals does not exist ?
d) write the electronic configuration of the following .
i) Na
ii) Cl
iii) O2-
iv) Ca2+
v) Cu
e) How many s-electron , p-electrons and d-electrons present in an element having atomic number 24 and also find out the number of unpaired electrons present in it .
f) An electron is present in one of the 3d – orbitals . Give the possible values of n , l, and ml for this electron .
Or
Why cations are smaller and anions are larger in radius than that of their parent atoms .
4. Answer the following questions
a) Define Ionisation enthalpy of an element . What are the factors on which it depends . How does it varies
in the in periodic table .
b) Why Ionisation enthalpy of nitrogen is greater than oxygen .
c) Why electron gain enthalpy of Flourine is less thsn Chlorine.
d) Why noble gases have almost zero electron gain enthalpy .
e) Write some charateristics of transitional element .
Published by LOKESH CHANDRA DAS