Tier Tinggi, Kimia-saja: tentukan konsentrasi asam dari data RP2
Diperkenalkan| English | Makna |
|---|---|
| known concentration/nəʊn ˌkɒnsənˈtreɪʃn/ | konsentrasi diketahui |
| titration concentration/taɪˈtreɪʃn ˌkɒnsənˈtreɪʃn/ | konsentrasi dari titrasi |
What would explain this observation?
- Higher Tier: A known sodium hydroxide solution can determine an unknown sulfuric-acid concentration. The acid amount is half the alkali amount because the equation requires two NaOH per H₂SO₄.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- For 2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O, n(acid)=n(NaOH)/2. First calculate alkali amount as concentration times pipetted volume in dm³. Divide by two, then divide acid amount by mean acid titre in dm³. Convert acid molar concentration to mass concentration by multiplying by its molar mass. For supplied H=1, S=32 and O=16, H₂SO₄ has molar mass 98 $\dfrac{\text{g}}{\text{mol}}$.
- known concentration 已知浓度: The supplied concentration of a reference solution used in the calculation; titration concentration 滴定求得浓度: A concentration inferred from reacting amounts and measured solution volumes.
Untuk 2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O, bagaimana hubungan jumlah asam dan basa?
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Persamaan 2NaOH + H2SO4 menunjukkan 2 mol basa per mol asam, sehingga jumlah asam adalah SETENGAH dari jumlah basa. Jumlah yang sama bertentangan dengan persamaan yang setara.
Pasangkan setiap istilah teknis dengan maknanya yang tepat.
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Gunakan definisi untuk membedakan besaran dan proses yang terkait.
Choose evidence that can test it
- The acquired handbook PDF page 35 correctly states the equation and the 2:1 ratio, but prints a reversed half-mole statement afterwards. The correct inference is acid moles = half alkali moles. The balanced equation gives the correct amount relationship. The common-tier RP2 task still concerns accurate reacting volumes, while this numerical determination is Higher-only.
- Use the measured accurate mean from the student’s actual supervised task, including the stated trial selection. Record known solution concentration and volume, convert cm³ to dm³, and label each chemical’s amount. If the question supplies different acid identity or coefficient ratio, change the calculation accordingly. A calculated concentration is not a direct burette reading.
Dua kebiasaan manakah yang membuat penyelidikan atau model dalam kasus ini lebih dapat dipertanggungjawabkan?
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Menyatakan kondisi dan asumsi memungkinkan orang lain mengulangi pekerjaan persis seperti itu, dan mencatat bukti pendukung memungkinkan mereka memeriksa kesimpulan. Menyembunyikan hasil yang bertentangan menghilangkan bukti yang dapat menentang kesimpulan yang salah, dan satu pengukuran tidak pernah dapat menetapkan klaim yang lebih luas.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: 25.0 cm³ NaOH at 0.100 $\dfrac{\text{mol}}{\text{dm}^3}$ contains 0.00250 mol. Acid amount=0.00125 mol. With acid mean titre 12.50 cm³, acid concentration=0.00125/0.01250=0.100 $\dfrac{\text{mol}}{\text{dm}^3}$. Mass concentration=0.100×98=9.80 $\dfrac{\text{g}}{\text{dm}^3}$. Both units describe the same solution using different quantities.
An inferred H₂SO₄ concentration is 0.150 $\dfrac{\text{mol}}{\text{dm}^3}$. With molar mass 98 $\dfrac{\text{g}}{\text{mol}}$, find its mass concentration. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
Konsentrasi H₂SO₄ yang disimpulkan adalah 0.150 mol per dm³. Dengan massa molar 98 g per mol, tentukan konsentrasi massanya.
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Hasilnya adalah 14.7 g per dm³. Diketahui: c = 0.150 mol per dm^3; massa molar 98 g per mol. Konsentrasi massa = c x M = 0.150 x 98 = 14.7 g per dm^3. Konsentrasi molar dan konsentrasi massa menggambarkan larutan yang sama dalam satuan berbeda.
Check the conclusion and its limits
- Do not multiply the alkali amount by two for this acid. Do not use centimetre-cubed volumes without conversion when concentration uses dm³. The result assumes the stated pure-solution reaction, correct endpoint and sufficiently accurate measurements.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
The handbook’s printed half-mole statement overrides its correctly balanced equation. This claim is false: The balanced equation is the authority for the mole ratio. A misremembered "half" comment cannot override 2NaOH + H2SO4 - the coefficients are fixed by conservation of atoms.
Higher Tier, Chemistry-only: determine acid concentration from RP2 data: The acquired handbook PDF page 35 correctly states the equation and the 2:1 ratio, but prints a reversed half-mole statement afterwards. The correct inference is acid moles = half alkali moles. The balanced equation gives the correct amount relationship. The common-tier RP2 task still concerns accurate reacting volumes, while this numerical determination is Higher-only.
Pernyataan setengah mol yang dicetak dalam buku panduan mengesampingkan persamaan setara yang benar.
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Persamaan yang setara adalah otoritas utama untuk rasio mol. Komentar "setengah" yang salah ingat tidak dapat mengesampingkan 2NaOH + H2SO4 - koefisien ditentukan secara mutlak oleh hukum kekekalan atom.
Konsentrasi yang disediakan dari larutan referensi yang digunakan dalam perhitungan: tuliskan istilah teknis.
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konsentrasi yang diketahui berarti konsentrasi yang disediakan dari larutan referensi yang digunakan dalam perhitungan.