1) A * explanation *less dense means light, so we use the upward dispalcement method( see notes blog )
so, reject option B. B is for heavy gases ( downward displacement method )
option C is for insoluble gases.
2) C
* explanation *
when particles at 50'C ( liquid ) becomes 120'C ( gases ),the energy of the particles increases, the spacing between the particles becomes far apart and hence the attractive forces between the particles decreases.
3) C* explanation *81 is nucleon number ( proton + neutrons ) / atomic mass37 is proton number ( proton = electron )therefore, 81-37= 44 neutrons.
4) C* explanation *Element X has a valency of +1Element Y has a valency of -2
therefore, when you use the criss-cross method, the formula is X2Y1
5) D
* explanation *
Element Q has 4 valence electrons
---> group 4 ( since number of valece electrons = group number )
Hydrogen and chlorine are non-metals.
So, non-metal & non-metal = covalent compound.
properties of covalent compound = low melting point ( see notes blog )
6) D
* explanation *look at what is given to you: you have 0.3 moles of C3H8.to find volume of gaseous productsso, which is the product they want? from the question, there is CO2 and H2O?answer: look at the state symbols, CO2 is in (g) state!!!mole ratio of C3H8 : CO2 is 1: 3no. of moles ofC3H8 = 0.1,1unit = 0.1,3 units = 0.1X 3 = 0.3 moles(please dont be careless and choose option B!! we have only found CO2's mole, the question wants VOLUME ) so,using P.K.X fav sentence: 1 mole of any gas = 24 dm3 at r.t.p,so, 0.3 mole = 0.3 X 24 = 7.2 dm3
7) B
* explanation *
during the process of neutralization, the temperature will increase ( see notes blog )that is why options C and D are out!now, when neutralization finishes, the ecess alkali added will make the temperature of the solution back to room temperature. Hence a decreasing gradient.
8) B
option A: when a more concentrated acid is used, the gradient of the graph will be steeper instead of gentle because the rate of reaction is faster.option C: when fewer amounts of reactant is used, the amount of CO2 produced will be less. So, it will not reached the same level as graph 1.option D: when powdered reactant is used, speed of reaction should increase, instead of decrease!
9) B
* explanation *
option A, D are out because all potassium salts are soluble!
remember the K-N-N-Na theory.
option C is out. Potassium sulphate is a salt, not a base.
answer is potassium carbonate neutralises the acid.
10) C
* explanation *
when halogen is Y added to X and Z, there is no reaction, this means that Y is the least reactive.
so, down the group of 7, reactivity decreases, so, Br- is the least reactive.
so, Y = Br-
if X can displace Y and Z, then X is the most reactive.
so, X = Cl-
11) B
12) D
* explanation *option A: coke is not used to oxidised slag!! coke is used to burn to give carbon dioxide and carbon monoxide!
option B: limestone is used to decomposed to form calcium oxide and carbon dioxide.
the calcium oxide is used to neutralise slag.
option C: molten iron is heavier, so it is at the bottom, and not floats on the slag!
13) D
14) B
15) A ( see textbook for the uses of cracking )
16) A
* explanantion *
in the complete combustion of organic compounds, only carbon dioxide and water are formed.
17) D
18) C
* explanation *
only compounds with C=C bonds will decolourise aqueous brmine.
other C= structure will not decompose aqueous bromine.
19) C ( see textbook )
20) D* explanation *polyester = many units of ester group.
Terylene contains ester linkage.Nylon contains amide linkage.Poly(ethene) contains many units of ethene .Protein contains amide linkage.
