HSSC chemistry

Written by Dr. Ayesha Nadeem (Chemistry)

PIEAS · کیمیا · 34 سوالات

نام: ____________________ تاریخ: ____________

The atomic number of carbon is:
- A 12
- B 14
- C 6
- D 8
The number of moles in 36 g of water (molar mass 18 g/mol) is:
- A 0.5
- B 18
- C 2
- D 4
The pH of a neutral solution at 25°C is:
- A 7
- B 0
- C 1
- D 14
Avogadro's number is approximately:
- A 3.0 × 10⁸
- B 6.02 × 10²³
- C 6.02 × 10²⁰
- D 1.6 × 10⁻¹⁹
The number of valence electrons in a sodium atom (1s² 2s² 2p⁶ 3s¹) is:
- A 11
- B 8
- C 1
- D 2
The general formula of the alkanes is:
- A CₙH₂ₙ₊₂
- B CₙH₂ₙ₋₂
- C CₙH₂ₙ
- D CₙHₙ
The bond in sodium chloride is:
- A Covalent
- B Ionic
- C Hydrogen bond
- D Metallic
The oxidation number of manganese in KMnO₄ is:
- A +2
- B +4
- C +7
- D −1
Boyle's law states that at constant temperature the pressure of a gas is:
- A Inversely proportional to its volume
- B Proportional to its volume
- C Proportional to the square of its volume
- D Independent of its volume
A catalyst changes a reaction by:
- A Increasing the yield only
- B Becoming a product
- C Increasing its rate without being used up
- D Lowering the temperature
The hybridisation of carbon in methane is:
- A sp³
- B sp
- C sp³d
- D sp²
The shape of the ammonia molecule is:
- A Trigonal pyramidal
- B Linear
- C Planar triangle
- D Tetrahedral
In the reaction N₂ + 3H₂ ⇌ 2NH₃, raising the pressure shifts the equilibrium toward:
- A No change
- B Ammonia
- C Nitrogen
- D Hydrogen
The pH of a 0.01 M solution of hydrochloric acid is:
- A 12
- B 1
- C 2
- D 0.01
Oxidation is the:
- A Gain of neutrons
- B Loss of electrons
- C Gain of electrons
- D Loss of protons
In the electrolysis of brine, chlorine gas is formed at the:
- A Container wall
- B Salt bridge
- C Anode
- D Cathode
The functional group of an alcohol is:
- A −NH₂
- B −COOH
- C −OH
- D −CHO
The IUPAC name of CH₃CH₂OH is:
- A Methanol
- B Ethanol
- C Propanol
- D Ethanal
The molarity of a solution made by dissolving 4 g of NaOH (molar mass 40 g/mol) in 500 mL of solution is:
- A 0.1 M
- B 0.2 M
- C 0.8 M
- D 2 M
The number of structural isomers of butane (C₄H₁₀) is:
- A 4
- B 1
- C 3
- D 2
The most electronegative element is:
- A Chlorine
- B Fluorine
- C Oxygen
- D Nitrogen
Across a period of the periodic table from left to right, the atomic radius generally:
- A Stays the same
- B Increases
- C Doubles
- D Decreases
The number of sigma bonds in an ethene molecule (C₂H₄) is:
- A 4
- B 6
- C 2
- D 5
Water has a higher boiling point than hydrogen sulfide because of:
- A Metallic bonding
- B A larger mass
- C Hydrogen bonding
- D Ionic bonding
Avogadro's law says that equal volumes of gases at the same temperature and pressure contain:
- A The same density
- B The same mass
- C The same number of atoms of each element
- D The same number of molecules
For an exothermic reaction the enthalpy change ΔH is:
- A Positive
- B Negative
- C Zero
- D Infinite
The effect of a catalyst on the value of the equilibrium constant is that it:
- A Doubles it
- B Increases it
- C Decreases it
- D Does not change it
The mass of 0.5 mol of calcium carbonate (molar mass 100 g/mol) is:
- A 100 g
- B 50 g
- C 200 g
- D 5 g
An ionic compound conducts electricity when it is:
- A Solid
- B Cold
- C Molten
- D A powder
The molecular formula of benzene is:
- A C₆H₁₂
- B C₆H₁₄
- C C₅H₆
- D C₆H₆
The reaction of methane with chlorine in ultraviolet light is a:
- A Elimination reaction
- B Condensation reaction
- C Substitution reaction
- D Addition reaction
Which of these is a weak acid?
- A Acetic acid
- B Hydrochloric acid
- C Sulfuric acid
- D Nitric acid
The percentage of oxygen by mass in water (H = 1, O = 16) is about:
- A 88.9%
- B 11.1%
- C 50%
- D 16%
In an electrochemical cell, reduction takes place at the:
- A Cathode
- B Wire
- C Anode
- D Salt bridge

جوابی کلید

1. C, 2. C, 3. A, 4. B, 5. C, 6. A, 7. B, 8. C, 9. A, 10. C, 11. A, 12. A, 13. B, 14. C, 15. B, 16. C, 17. C, 18. B, 19. B, 20. D, 21. B, 22. D, 23. D, 24. C, 25. D, 26. B, 27. D, 28. B, 29. C, 30. D, 31. C, 32. A, 33. A, 34. A

Carbon has 6 protons.
Moles = mass ÷ molar mass = 36 ÷ 18 = 2.
Pure water has equal H⁺ and OH⁻ concentrations at pH 7.
One mole contains this number of particles.
Only the 3s electron is in the outer shell.
Alkanes are saturated hydrocarbons, such as CH₄ and C₂H₆.
Sodium transfers an electron to chlorine.
Potassium is +1 and four oxygens are −8, so manganese is +7.
P₁V₁ = P₂V₂ at a fixed temperature.
It gives an easier path for the reaction.
Carbon forms four single bonds in methane.
Nitrogen has three bonds and one lone pair.
There are fewer gas molecules on the right.
pH = −log 0.01 = 2.
Oxidation is loss of electrons.
Chloride ions are oxidised at the anode.
Alcohols have a hydroxyl group.
The two carbon chain gives eth and the OH group gives ol.
4 ÷ 40 = 0.1 mol in 0.5 L, which is 0.2 M.
They are butane and 2-methylpropane.
Fluorine has the highest electronegativity.
The nuclear charge rises while the shell stays the same.
There are four C−H bonds and one C−C sigma bond.
Water molecules form hydrogen bonds with each other.
The number of molecules is the same for every gas.
Heat is released, so the enthalpy of the system falls.
A catalyst speeds up the forward and backward reactions equally, so the constant stays the same.
Mass = 0.5 × 100 = 50 g.
The ions can move only when molten or dissolved.
Benzene has six carbon atoms and six hydrogen atoms.
A hydrogen atom is replaced by a chlorine atom.
Acetic acid ionises only slightly in water.
The share is 16 ÷ 18 × 100.
Reduction is gain of electrons at the cathode.