## Chemistry Study Mode

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Question 1
A
both processes are exothermic
B
both processes are endothermic
C
the dissolution of metallic sodium is endothermic
D
the dissolution of metallic sodium is exothermic
E
the dissolution of sodium chloride is explosive
Explanation.

When small quantities of sodium metal is added to water, there is an exothermic reaction, and they react to form sodium hydroxide and hydrogen.

Question 2
A
5cm3
B
10cm3
C
20cm3
D
25cm3
E
50cm3
Explanation.

$$2NaOH + H_{2}SO_{4} = Na_{2}SO_{4} + 2H_{2}O$$
V x 0.5M = 2(10 x 1.25)
0.5V = 2 x 12.5
0.5V = 25
V = $$\frac{25}{0.5}$$ = $$50cm^{3}$$

Question 3
A
acetic acid and ethene
B
ethanoic acid and ethene
C
methanoic acid and ethylene
D
ethanol and ethene
E
acetic acid and ethylene
Explanation.

The IUPAC id for $$CH_{3}COOH$$ is Acetic acid, while for $$C_{2}H_{4}$$ is ethene.

Question 4
A
the temperature at which its vapour pressure equals the atmospheric pressure
B
the temperature at which bubbles begin to form
C
the temperature at which the vapour pressure equals 1 temperature
D
the temperature at which the rate of condensation of vapour equals the rate of vaporisation of the liquid
E
the temperature at which the space above the liquid is saturated
Explanation.

The normal boiling point is the temperature at which the vapour pressure is equal to the standard sea-level atmospheric pressure which is 760 mm [29.92 inches] of mercury.

Question 5
A
Na2CO3.10H2
B
NaNO3
C
CuSO4
D
CaCl2
E
Na2SO4.10H2
Explanation.

Calcium chloride is a deliquescent substance. It attracts water from the atmosphere and then forms a solution.

Question 6
A
0.3g
B
1.5g
C
2.4g
D
3.0g
Explanation.

Molar conc. =no.of molesVol in dm3
Vol=250cm3= 0.25dm3
Molar conc=0.5M
No of moles=molar conc *Vol in dm3
=0.5*0.25
=0.125mole of HCl
2moles of HCl → Mole of Mg
0.125 mole →(0.125*1)/2
=0.0625mole of Mg
Reacting mass=no of moles* molar mass
Mg=24
Mass=0.0625*24
=1.5g

Question 7
A
Ice at -10C
B
Ice at 0C
C
Water at 100C
D
Steam at 100C
Explanation.

The gaseous state of matter has the most disorderly arrangement of particles. Hence, steam (water in gaseous form) is the most disorderly arrangement on the list.

Question 8
A
14
B
12
C
11
D
10
Explanation.

K$$_{2}$$Cr$$_{2}$$O$$_{7}$$ + HCl  → Cl$$_{2}$$ + KCl + CrCl$$_{3}$$ + H$$_{2}$$O

Balancing the equation, we have

K$$_{2}$$Cr$$_{2}$$O$$_{7}$$ + 14HCl → 3Cl$$_{2}$$ + 2KCl + 2CrCl$$_{3}$$ + 7H$$_{2}$$O

Question 9
A
2.029 * 10-3mol dm-3
B
1.414 * 10-3mol dm-3
C
2.029 * 10-5mol dm-3
D
1.414 * 10-5mol dm-3
Explanation.

In order to calculate this, it suffices to calculate the solubility of Ag, so as to know the amount lost.

$$K_{sp} = [Ag^{+}][Cl^{-}]$$

Let the solubilty of Ag and Cl = d

$$2 \times 10^{-10} = d \times d= d^{2}$$

$$d = \sqrt{2\times10^{-10}}$$

= $$1.414 \times 10^{-5}moldm^{-3}$$

Question 10
A
Pale green
B
Pale red
C
Brown
D
Colourless
Explanation.

A reaction between Iron (iii) chloride and Hydrogen sulphide leads to the reaction

2FeCl3(aq) + H2S(g) → 2FeCl2(aq) + 2HCl(aq) + S(s)

The colour change is from REDDISH BROWN to PALE GREEN.