CHEMISTRY Kertas 1

Table 3 shows the proton number of elements X, Y and Z.

Jadual 3 menunjukkan nombor proton unsur X, Y dan Z.

Which of the following is true about the elements?

Antara berikut, yang manakah benar tentang unsur-unsur tersebut?

• The size of X atom is the largest followed by Y and Z

  Saiz atom X adalah terbesar dikuti oleh Y dan Z

• Have same number of shells occupied with electrons

  Mempunyai bilangan petala berisi electron yang sama

• The reactivity decreases in the order of X, Y and Z

  Kereaktifan semakin berkurang dalam turutan X, Y dan Z

• Reacts with oxygen gas to form basic oxide

  Bertindak balas dengan gas oksigen untuk membentuk oksida bes

Answer explanation

In the statement "The element X has a higher proton number than both elements Y and Z," the term "proton number" refers to the atomic number of an element, which is equal to the number of protons in the nucleus of its atom. The atomic number determines the identity of an element and its position in the periodic table.

So, if X has a higher proton number than both Y and Z, it means that X is positioned to the left of Y and Z in the periodic table because atomic numbers increase from left to right. Elements to the left generally have higher proton numbers than those to the right.

Berapakah kepekntan asidX di dalam pipet?

• 0.1 mol dm-3

• 0.2 mol dm-3

• 1.0 mol dm-3

• 2.0 mol dm-3

Answer explanation

Untuk menjawab soalan itu, saya memerlukan maklumat lanjut mengenai eksperimen atau situasi yang sedang dibincangkan. Apakah Anda boleh memberikan lebih banyak konteks tentang keadaan di mana kepekatan asid X di dalam pipet diperlukan? Dengan maklumat tambahan, saya akan cuba membantu menjawab soalan anda.

Diagram 3 shows the electron arrangement of atoms of element X and y. These elements are placed in the same period in the Periodic Table of Elements. Which of the following explain the statement?

• Have the same chemical properties

• Have three shells filled with electrons

• Have eight electrons in their second shell

• Have the same number of valence electrons

Answer explanation

1. 1. Comparing the number of electron shells in elements X and Y and how it affects their chemical behavior.

3. 2. Analyzing the arrangement of electrons in the outermost shell (valence shell) of elements X and Y and how it relates to their reactivity or bonding tendencies.

5. 3. Discussing any similarities or differences in the electron configuration of elements X and Y and how they align with periodic trends such as electronegativity, atomic size, or ionization energy.

Which cation Present in hard water?

• Md

• Zn₂

• Pb₂

• Sn₂

Answer explanation

In hard water, the cations that are commonly present are calcium (𝐶𝑎₂+Ca₂+) and magnesium (𝑀𝑔₂+Mg₂+) ions. These ions are typically dissolved in the water as a result of the water passing through or over mineral deposits containing calcium and magnesium compounds.

The presence of calcium and magnesium ions is what causes water to be "hard." These ions can form insoluble compounds with certain anions like carbonate (𝐶𝑂3₂−CO32−​) and sulfate (𝑆𝑂42−SO42−​), leading to the formation of scale deposits in pipes, appliances, and other water fixtures.

Berapakah peratus jisim karbon dalam sebatianX?

• 14.29%

• 16.67%

• 68.57%

• 85.71%

Diagram 4 shows the apparatus set-up for electrolysis of X. Which of the following is X?

• Sugar solution

• Cooking oil

• Kerosene

• Vinegar

Which of the following is correct about electron?

• Neutral subatomic Particle

• Has the same mass as Proton

• Involves in chemical reaction

• Located in the nucleus of an atom

Excess metal X reacts with 50 cm³ of 1.0 mol dm^-3 asid Y produces 1.2 dm³ of hydrogen gas.

Which of the following is the possible chemical equation for this reaction?

[Relative atomic mass: H:1, Volume of 1 mol of gas in room condition : 24 dm³]

Logam X berlebihan bertindak balas dengan 50 cm³ asid Y 1.0 mol dm^-3 menghasilkan

1.2 dm³ gas hidrogen.

Antara berikut, yang manakah persamaan kimia yang mungkin untuk tindak balas ini?

[Jisim atom relatif: H: 1, Isipadu 1 mol gas dalam keadaan bilik : 24 dm³]

• Mg + 2HNO₃ → MgCl₂ + H₂

• Mg + H₂SO₄ → MgSO₄ + H₂

• 2Al + 6HCl → 2AlCl₃ + 3H₂

• 2Al + 6CH₃COOH → 2(CH₃COO)3Al + 3H₂

Diagram 2 shows the energy profile diagram for the reaction between P and Q. The heat of reaction, ΔH for the reaction is -Z kJ mol-1. Which of the following represent the value of Z?

• x

• y

• (x-y)

• (y-x)

How many moles of iron(III) ions are there in 16g of iron(III) oxide? [Relative atomic mass: O = 16, Fe = 56]

• 0.20 mol

• 0.22 mol

• 0.30 mol

• 0.66 mol

Answer explanation

The molar mass of iron(III) oxide (𝐹𝑒2𝑂3Fe2​O3​) can be calculated as follows:

𝑀𝑜𝑙𝑎𝑟 𝑀𝑎𝑠𝑠𝐹𝑒2𝑂3=(2×𝑀𝑜𝑙𝑎𝑟 𝑀𝑎𝑠𝑠𝐹𝑒)+(3×𝑀𝑜𝑙𝑎𝑟 𝑀𝑎𝑠𝑠𝑂)MolarMassFe2​O3​​=(2×MolarMassFe​)+(3×MolarMassO​)

Given that the relative atomic masses are 𝑂=16O=16 and 𝐹𝑒=56Fe=56, we can substitute these values into the equation:

𝑀𝑜𝑙𝑎𝑟 𝑀𝑎𝑠𝑠𝐹𝑒2𝑂3=(2×56)+(3×16)MolarMassFe2​O3​​=(2×56)+(3×16) 𝑀𝑜𝑙𝑎𝑟 𝑀𝑎𝑠𝑠𝐹𝑒2𝑂3=112+48MolarMassFe2​O3​​=112+48 𝑀𝑜𝑙𝑎𝑟 𝑀𝑎𝑠𝑠𝐹𝑒2𝑂3=160 𝑔/𝑚𝑜𝑙MolarMassFe2​O3​​=160g/mol

Now that we know the molar mass of iron(III) oxide is 160 𝑔/𝑚𝑜𝑙160g/mol, we can calculate the number of moles of iron(III) oxide (𝐹𝑒2𝑂3Fe2​O3​) present in 16g using the formula:

𝑚𝑜𝑙𝑒𝑠=𝑚𝑎𝑠𝑠𝑚𝑜𝑙𝑎𝑟 𝑚𝑎𝑠𝑠moles=molarmassmass​

Substituting the given values:

𝑚𝑜𝑙𝑒𝑠=16𝑔160 𝑔/𝑚𝑜𝑙moles=160g/mol16g​ 𝑚𝑜𝑙𝑒𝑠=110 𝑚𝑜𝑙moles=101​mol

Since each formula unit of iron(III) oxide contains two iron(III) ions (𝐹𝑒3+Fe3+), the number of moles of iron(III) ions present is twice the number of moles of iron(III) oxide:

𝑚𝑜𝑙𝑒𝑠𝐹𝑒3+=2×𝑚𝑜𝑙𝑒𝑠𝐹𝑒2𝑂3molesFe3+​=2×molesFe2​O3​​ 𝑚𝑜𝑙𝑒𝑠𝐹𝑒3+=2×110 𝑚𝑜𝑙molesFe3+​=2×101​mol 𝑚𝑜𝑙𝑒𝑠𝐹𝑒3+=15 𝑚𝑜𝑙molesFe3+​=51​mol

Therefore, there are 1551​ moles of iron(III) ions (𝐹𝑒3+Fe3+) in 16g of iron(III) oxide.