Ayomide Daniel

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Ayomide provided a contribution 10 months ago

Question 301 | Chemistry Past Questions

its D because when sodium carbonate reacts with calcium hydrogentrioxocarbonate it gives sodium hydrogentrioxocarbonate and calcium trioxocarbonate.it can remove temporal hardness and also permanent hardness here is the equation when(Na2CO3+Ca(HCO3) it will form NaHCO3aq +CaCO3s.

Ayomide provided a contribution 10 months ago

Question 319 | Chemistry Past Questions

Hcl acid is used as test for both carbonate and sulphide eg Caco3 2 Hcl ----> cacl2+H2O+CO2

PbS+2Hcl ------>Pbcl2+H2S

the liberation of CO2 and hydrogen sulphide are used to identify them respectively.

But in the test for sulphate barium chloride is added

the unkown acidified solution . White precipitate indicates the presence of sulphate ion

Conclusion

since the question said what can identify "just one of them" answer is A for barium chloride


Ayomide provided a contribution 10 months ago

Question 318 | Chemistry Past Questions

Zn (s)+ CuSO4(aq)----> ZnSO4(aq) +Cu(s)

in the eqn above zinc is the reducing agent . It displaced Cu from its soln cos its more electroposive than copper.

Conclusion (C) is d correct answer . D could have been the answer if they wrote that zinc is the reducing agent , because copper in some case can be a reducing agent


Ayomide provided a contribution 10 months ago

Question 305 | Chemistry Past Questions

The rate of diffusion of a gas is proportional to the square root of the density.
16 and 7 secs
36 or 6 will be proportional to
7/16 x 6
7/4 x 6
But volume of chlorine is twice that of oxygen. The rate of escape of chlorine is
2/1 x 7/4 x 6/1 = 7 x 3; = 21 sec

Ayomide provided a contribution 10 months ago

Question 288 | Chemistry Past Questions

The answer is D. Reason:when a piece metallic sodium is dropped into a beaker of water,the sodium reacts with water acording to the eqation 2Na+2H2O---2NaOH+H2

.the sodium begins to melt @ a temperature of 97.8 deg. Celcius(melting point of sodium).there is a great amount of heat given off at this moment(exothermic reaction).the heat in the surroundings ignites d hydrogen gas given off in d reaction and causes it to burn with a bright flame


Ayomide provided a contribution 10 months ago

Question 178 | Biology Past Questions

The part of the brain that controls involuntary or unconscious actions is the medulla oblongata,not the spinal cord.The spinal cord is just surrounded by 8 pairs of menenges.

Ayomide provided a contribution 10 months ago

Question 239 | Chemistry Past Questions

Firstly, Duralumin is an alloy consisting of ALUMINUM , COPPER , MANGANESE and MAGNESIUM. Duralumin is used in aircrafts/aeroplanes because it is stronger as compared to steel and also for the fact that it is lighter in weight. Hence makes it suitable for aviation purposes.

Ayomide provided a contribution 10 months ago

Question 238 | Chemistry Past Questions

NH4CL(aq), (i.e in aqueous form or ammonium chloride + water) is different from NH4CL(s), (i.e in dry crystal form). So since NH4CL(aq) contains water, you have to carefully ''EVAPORATE'' the water content first to get the solid crystal of NH4CL(s). Then, on further heating, the NH4CL(s) ''SUBLIMES'' to the cooler part of the container. So Yea, the correct option is D.

Ayomide provided a contribution 10 months ago

Question 225 | Chemistry Past Questions

relative molecular mass=vapour density *2

;rmm=45*2

=90

(CH2O)=90

(12+2+16)n=45

(30)n=90

n=90/30

n=3

the molecular formula=(C3H6O3)


Ayomide provided a contribution 10 months ago

Question 203 | Chemistry Past Questions

potassium aluminium tetraoxosulphate (VI) = K(ALSO4)2

after reaction its oxidizes to give SO4+2-=

Note that cations are postive and anions are negative


Ayomide provided a contribution 10 months ago

Question 188 | Chemistry Past Questions

mass given =2g

Vol given =100cm³

M=m/mm

mole=mass/molar mass.

Molar mass=40gmol-¹

Na+O+H=23+16+1=40gmol-¹

Molar conc=mass×1000cm³/molar mass×vol

Molar conc of the solution=2×1000/40×100

Molar conc=0.5mol/dm³


Ayomide provided a contribution 10 months ago

Question 186 | Chemistry Past Questions

Alkenes can declourise bromine water, but Alkanes cannot. The slideshow shows the process. Other addition reaction of alkenes: hydrogen can be added to a C=C double bond.

Ayomide provided a contribution 10 months ago

Question 206 | Chemistry Past Questions

Examples of deliquescent substances

sodium hydroxide
Iron(III)chloride
potassium hydroxide
calcium chloride✔
magnesium chloride
phosphorus (V) oxide
silica gel


Ayomide provided a contribution 10 months ago

Question 195 | Chemistry Past Questions

From the diagram,

55°C = 7 moles; 40°C = 6 moles.

Amount of solute deposited = 7 - 6 = 1 mole.

1000 cm3 = 1 mole

200 cm3 = x

x = 200×11000
= 0.20 mole.