Remed Uts Genap Xi IPA-2 Smanio (The Number Of Students Absent 11-20)

1. Lakmus biru akan menjadi merah apabila dicelupkan dalam larutan … .

NaOH

Ba(NO3)2

(NH4)2SO4

K2CO3

CaCl2

Lakmus biru akan menjadi merah apabila dicelupkan dalam larutan (NH4)2SO4.

Explanation

Lakmus biru akan menjadi merah apabila dicelupkan dalam larutan (NH4)2SO4.

2. Jika ke dalam 50 mL larutan penyangga dengan pH = 5 ditambahkan 50 mLakuades, maka ...

PH akan turun sedikit

PH akan naik sedikit

PH turun drastis

PH naik drastis

PH tidak berubah

When 50 mL of water is added to a 50 mL buffer solution with a pH of 5, the pH will not change. This is because the buffer solution is able to resist changes in pH by maintaining a relatively constant concentration of both the acid and its conjugate base. The addition of water does not introduce any new acid or base species that would alter the equilibrium of the buffer system, thus the pH remains the same.

Explanation

When 50 mL of water is added to a 50 mL buffer solution with a pH of 5, the pH will not change. This is because the buffer solution is able to resist changes in pH by maintaining a relatively constant concentration of both the acid and its conjugate base. The addition of water does not introduce any new acid or base species that would alter the equilibrium of the buffer system, thus the pH remains the same.

3. Jika pH larutan 0,01 M suatu asam lemah HA adalah 3,5, maka tetapan asam (Ka) adalah … .

1 × 10–3

2 × 10–3

1 × 10–5

1 × 10–7

1 × 10–8

The pH of a solution is a measure of its acidity, with lower pH values indicating higher acidity. In this question, the pH of a 0.01 M solution of a weak acid HA is given as 3.5. Since the pH is less than 7, it indicates that the solution is acidic. The Ka (acid dissociation constant) is a measure of the extent to which an acid dissociates in water. The lower the Ka value, the weaker the acid. Therefore, since the solution is acidic and the acid is weak, the Ka value must be relatively small. Among the given options, 1 × 10–5 is the smallest value, indicating the weakest acid and hence the correct answer.

Explanation

The pH of a solution is a measure of its acidity, with lower pH values indicating higher acidity. In this question, the pH of a 0.01 M solution of a weak acid HA is given as 3.5. Since the pH is less than 7, it indicates that the solution is acidic. The Ka (acid dissociation constant) is a measure of the extent to which an acid dissociates in water. The lower the Ka value, the weaker the acid. Therefore, since the solution is acidic and the acid is weak, the Ka value must be relatively small. Among the given options, 1 × 10–5 is the smallest value, indicating the weakest acid and hence the correct answer.

4. Jika 100 mL larutan HCl 0,1 M dicampurkan dengan 50 mL larutan NH3 0,3 M (Kb = 10–5), maka pH larutan yang terjadi adalah … .

9 + log 3

9 + log 5

9 – log 5

8 – log 2

8 + log 5

The given question involves the mixing of an acidic solution (HCl) with a basic solution (NH3). When HCl and NH3 react, they form NH4Cl, which is a salt. NH4Cl is a strong electrolyte that dissociates completely in water, producing NH4+ and Cl- ions. The NH4+ ions can act as a weak acid, while the Cl- ions do not affect the pH. Therefore, the resulting solution will be slightly acidic. The pH of the solution can be calculated using the equation pH = -log[H+]. Since NH4+ is a weak acid, the concentration of H+ ions can be determined using the Kb value of NH3. By calculating the concentration of H+ ions and taking the negative logarithm, the pH of the resulting solution can be found to be 8 + log 5.

Explanation

The given question involves the mixing of an acidic solution (HCl) with a basic solution (NH3). When HCl and NH3 react, they form NH4Cl, which is a salt. NH4Cl is a strong electrolyte that dissociates completely in water, producing NH4+ and Cl- ions. The NH4+ ions can act as a weak acid, while the Cl- ions do not affect the pH. Therefore, the resulting solution will be slightly acidic. The pH of the solution can be calculated using the equation pH = -log[H+]. Since NH4+ is a weak acid, the concentration of H+ ions can be determined using the Kb value of NH3. By calculating the concentration of H+ ions and taking the negative logarithm, the pH of the resulting solution can be found to be 8 + log 5.

5. Sebanyak 50 mL larutan CH3COOH 0,1 M (Ka = 10^–5) direaksikan dengan 50 mL larutan KOH 0,1 M. pH campuran yang terjadi adalah …

3

6-log7

8+log7

9-log7

9+log7

The given question involves the reaction between a solution of CH3COOH (acetic acid) and KOH (potassium hydroxide). Acetic acid is a weak acid and potassium hydroxide is a strong base. When they react, they undergo a neutralization reaction to form water and a salt (potassium acetate). The pH of the resulting mixture depends on the concentration of the salt formed. In this case, the concentration of the salt is not provided, so we cannot determine the exact pH. However, the answer choice "8+log7" suggests that the pH is slightly basic, as the logarithm of a number greater than 1 would be positive.

Explanation

The given question involves the reaction between a solution of CH3COOH (acetic acid) and KOH (potassium hydroxide). Acetic acid is a weak acid and potassium hydroxide is a strong base. When they react, they undergo a neutralization reaction to form water and a salt (potassium acetate). The pH of the resulting mixture depends on the concentration of the salt formed. In this case, the concentration of the salt is not provided, so we cannot determine the exact pH. However, the answer choice "8+log7" suggests that the pH is slightly basic, as the logarithm of a number greater than 1 would be positive.

6. Salah satu contoh larutan penyangga adalah larutan yang mengandung campuran...

HNO3 dan NaNO3

H2CO3 dan NaHCO3

NaOH dan NaCl

NH4OH dan HCl

CH3COOH dan NaOH

Larutan penyangga terbentuk ketika terdapat campuran asam lemah dan basa konjugatnya. H2CO3 adalah asam lemah dan NaHCO3 adalah basa konjugatnya. Oleh karena itu, campuran H2CO3 dan NaHCO3 dapat membentuk larutan penyangga.

Explanation

Larutan penyangga terbentuk ketika terdapat campuran asam lemah dan basa konjugatnya. H2CO3 adalah asam lemah dan NaHCO3 adalah basa konjugatnya. Oleh karena itu, campuran H2CO3 dan NaHCO3 dapat membentuk larutan penyangga.

7. 12 gram magnesium dimasukkan dalam larutan HCl sehingga habis bereaksi. Mg +2HCl → MgCl₂ + H₂ Jika gas hidrogen yang terjadi diukur pada suhu dan tekanan standar (STP), maka volume gas hidrogen tersebut adalah.....(Ar Mg = 24)

1,12 L

2,24 L

4,48 L

11,2 L

22,4 L

When magnesium reacts with hydrochloric acid, it produces magnesium chloride and hydrogen gas. According to the balanced chemical equation, 1 mole of magnesium reacts with 2 moles of hydrochloric acid to produce 1 mole of hydrogen gas. Since the molar volume of any gas at STP is 22.4 L, we can calculate the volume of hydrogen gas produced by dividing the number of moles of hydrogen gas by the molar volume. In this case, 1 mole of hydrogen gas is produced, so the volume of hydrogen gas is 1 * 22.4 L = 22.4 L. However, the question states that the 12 grams of magnesium completely reacts, which is less than 1 mole. Therefore, the volume of hydrogen gas produced will be less than 22.4 L. The only option that is less than 22.4 L is 11.2 L, so that is the correct answer.

Explanation

When magnesium reacts with hydrochloric acid, it produces magnesium chloride and hydrogen gas. According to the balanced chemical equation, 1 mole of magnesium reacts with 2 moles of hydrochloric acid to produce 1 mole of hydrogen gas. Since the molar volume of any gas at STP is 22.4 L, we can calculate the volume of hydrogen gas produced by dividing the number of moles of hydrogen gas by the molar volume. In this case, 1 mole of hydrogen gas is produced, so the volume of hydrogen gas is 1 * 22.4 L = 22.4 L. However, the question states that the 12 grams of magnesium completely reacts, which is less than 1 mole. Therefore, the volume of hydrogen gas produced will be less than 22.4 L. The only option that is less than 22.4 L is 11.2 L, so that is the correct answer.

8. Jika 2 L larutan natrium asetat (Ka= 10–5) mempunyai pH = 9, maka massa natrium asetat (CH3COONa) yang terdapat dalam larutan tersebut adalah … .(Ar C = 12, O = 16, dan Na = 23)

8,2 gram

16, 4 gram

82 gram

164 gram

1,64 gram

The given question is asking for the mass of sodium acetate (CH3COONa) present in the solution. The pH of the solution is given as 9, which means it is basic. Sodium acetate is a salt that can act as a weak base in water. The Ka value provided indicates that it is a weak acid. Since the solution is basic, it means that the acetate ion (CH3COO-) is the dominant species in the solution. To calculate the mass of sodium acetate, we need to find the moles of acetate ion present in the solution. From there, we can calculate the mass using the molar mass of sodium acetate. Unfortunately, without additional information, it is not possible to determine the mass of sodium acetate.

Explanation

The given question is asking for the mass of sodium acetate (CH3COONa) present in the solution. The pH of the solution is given as 9, which means it is basic. Sodium acetate is a salt that can act as a weak base in water. The Ka value provided indicates that it is a weak acid. Since the solution is basic, it means that the acetate ion (CH3COO-) is the dominant species in the solution. To calculate the mass of sodium acetate, we need to find the moles of acetate ion present in the solution. From there, we can calculate the mass using the molar mass of sodium acetate. Unfortunately, without additional information, it is not possible to determine the mass of sodium acetate.

9. Menurut teori asam-basa Bronsted-Lowry, H2O akan bersifat … .

Asam terhadap NH3

Asam terhadap HCl

Asam terhadap CH3COOH

Basa terhadap NH3

Asam terhadap H2S

H2O akan bersifat asam terhadap HCl berdasarkan teori asam-basa Bronsted-Lowry. Menurut teori ini, asam adalah zat yang dapat memberikan proton (H+), sedangkan basa adalah zat yang dapat menerima proton. Dalam reaksi antara H2O dan HCl, H2O akan memberikan proton (H+) kepada HCl, sehingga H2O berperan sebagai asam dan HCl berperan sebagai basa.

Explanation

H2O akan bersifat asam terhadap HCl berdasarkan teori asam-basa Bronsted-Lowry. Menurut teori ini, asam adalah zat yang dapat memberikan proton (H+), sedangkan basa adalah zat yang dapat menerima proton. Dalam reaksi antara H2O dan HCl, H2O akan memberikan proton (H+) kepada HCl, sehingga H2O berperan sebagai asam dan HCl berperan sebagai basa.

10. Jika diketahui Ka CH3COOH = 10^–5, maka pH larutan Ca(CH3COO)2 0,1 M adalah … .

5

5 - log 1,4

9

9 - log 1,4

9 + log 1,4

The given correct answer, 9 + log 1,4, suggests that the pH of the solution Ca(CH3COO)2 0,1 M can be calculated by adding 9 to the logarithm of 1,4. The pH of a solution can be determined by the concentration of hydrogen ions (H+). In this case, Ca(CH3COO)2 is a salt that dissociates into Ca2+ ions and 2 CH3COO- ions. Since CH3COOH is a weak acid, it partially dissociates into H+ and CH3COO-. The concentration of H+ ions can be determined by calculating the concentration of CH3COO- ions. By using the given Ka value of CH3COOH, the concentration of H+ ions can be determined, which can then be used to calculate the pH of the solution.

Explanation

The given correct answer, 9 + log 1,4, suggests that the pH of the solution Ca(CH3COO)2 0,1 M can be calculated by adding 9 to the logarithm of 1,4. The pH of a solution can be determined by the concentration of hydrogen ions (H+). In this case, Ca(CH3COO)2 is a salt that dissociates into Ca2+ ions and 2 CH3COO- ions. Since CH3COOH is a weak acid, it partially dissociates into H+ and CH3COO-. The concentration of H+ ions can be determined by calculating the concentration of CH3COO- ions. By using the given Ka value of CH3COOH, the concentration of H+ ions can be determined, which can then be used to calculate the pH of the solution.