PRE-UPS K5F

1. A magnesium ion has

• 24 protons and 26 electrons
• 12 protons and 13 electrons
• 12 protons and 10 electrons
• 24 protons and 22 electrons

2. Which of the following contains only empirical formulas?

• C₃H₈, N₂O₄, H₂O
• C₃H₆, NO₂, H₂O₂
• C₅H₁₀, N₂O₄, H₂O₂
• C₅H₁₂, NO₂, H₂O

3. Some distilled water is added to 0.5 mol HCl to made up a liter of solution. Molarity of the new solution is

• 2.0 M
• 0.25 M
• 0.5 M
• 0.4 M

4. What is the mole fraction of substance A in solution if 30 grams of Substance A is dissolved in 3.25 moles of Substance B? Given Molar Mass of substance A=30 g/moles.

• 0.765
• 0.902
• 0.098
• 0.235

5. A solution contains 56% hydrochloric acid by mass. This means that

• 1 litre of solution contains 56g of hydrochloric acid
• 1 litre of solution has a mass of 56% hydrochloric acid
• 1000g of solution contains 560g of hydrochloric acid
• 1000g of solution contains 56% hydrochloric acid

6. a, b, c and d are the coefficients for the balance chemical equation below. Identify the correct value for the coefficients

• A
• B
• C
• D

7. In an experiment, 0.02 mol magnesium strip is react with 0.03 mol hydrochloric acid as the following equation. Identify the limiting reactant and give your reason.

• magnesium because it is completely used up first
• magnesium because it is remained after the experiment
• hydrochloric acid because it is completely used up first
• hydrochloric acid because it is remained after the experiment

8. For Bohr’s atomic model, electron which moves at the first orbits from the nucleus would at the

• transition energy level
• excited state energy level
• highest energy level
• lowest energy level

9. What is the energy level of an electron which has -5.45x10⁻¹⁹ J of energy?

• 1
• 2
• 3
• 4

10. The diagram below shows lines of emission spectrum of hydrogen atom in Balmer series in the visible region. Select the transition of electron that gives rise to the line Q.

• n=2 to n=5
• n=4 to n=2
• n=4 to n=1
• n=5 to n=2