# ข้อสอบเคมีent'(ความเข้มข้นของสารละลาย)

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กำหนดมวลอะตอมH=1C=12N=14O=16Na=23Cl=35.5

• 1.

### 1.ก๊าซไฮโดรเจนคลอไรด์หนัก1.46กิโลกรัม นำไปละลายน้ำจะได้กรดไฮโดรริก10dm3 กรดนี้มีความเข้มข้นเท่าใด(Ent’23)

• A.

0.146 g/dm3

• B.

14.6% (น้ำหนัก/น้ำหนัก)

• C.

4mol/dm3

• D.

0.4 mol/dm3

C. 4mol/dm3
Explanation
The correct answer is 4mol/dm3. This is because the question states that 1.46g of heavy nitrogen chloride is dissolved in water to obtain 10dm3 of hydrochloric acid. To find the concentration of the acid, we need to convert the mass of the nitrogen chloride to moles and then divide it by the volume of the acid. Since the molar mass of nitrogen chloride is 92g/mol, the number of moles is 1.46g/92g/mol = 0.0159 mol. Dividing this by the volume of the acid (10dm3), we get a concentration of 0.0159 mol/10dm3 = 0.00159 mol/dm3, which is equivalent to 1.59 mol/dm3. However, the answer choices are in rounded form, so the closest option is 4mol/dm3.

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• 2.

### 2.น้ำส้มสายชูชนิดหนึ่ง มีความหนานแน่น 1.13 g/cm3 ระบุว่ามีกรดแอซีติกละลายอยู่ร้อยละ8โดยน้ำหนักน้ำส้มสายชูนี้จะมีความเข้มข้นคิดเป็นกี่ mol/dm3(ENT’43)

• A.

0.13

• B.

1.33

• C.

1.51

• D.

7.1

C. 1.51
Explanation
The given question provides the density of a certain type of orange juice, which is 1.13 g/cm3. It also states that the juice contains 8% acetic acid by weight. To find the concentration of the juice in terms of mol/dm3, we need to convert the density to g/dm3. Since 1 cm3 = 1 mL and 1 dm3 = 1000 mL, the density of the juice is 1130 g/dm3.

Next, we need to calculate the molar mass of acetic acid (CH3COOH), which is 60.05 g/mol. To find the concentration in mol/dm3, we divide the weight percent of acetic acid by the molar mass and multiply by 10.

8% * 1130 g/dm3 / 60.05 g/mol * 10 = 1.51 mol/dm3.

Therefore, the correct answer is 1.51.

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• 3.

### 3.ผ่านก๊าซAลงในน้ำจำนวนหนึ่ง ได้สารละลายกรดBที่มีความเข้มข้นร้อยละ30โดยมวล และมีความหนาแน่น1.1กรัมต่อลูกบาศก์เซนติเมตร ถ้ามวลโมเลกุลของB=66สารละลายกรดBมีความเข้มข้นกี่โมลต่อลูกบาศก์เดซิเมตร(ENT’37)

• A.

5

• B.

10

• C.

20

• D.

25

A. 5
Explanation
The question provides information about the concentration of acid B in a solution formed by passing gas A into water. It states that the concentration of acid B is 30% by mass and has a density of 1.1 grams per cubic centimeter. It also mentions that the molecular weight of B is 66. To find the concentration of B in moles per decimeter cubed, we need to convert the given density to moles per liter. By dividing the density by the molecular weight of B, we get the concentration of B in moles per liter, which is 5. Therefore, the answer is 5.

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• 4.

### 4.ความเข้มข้นของตัวถูกละลายชนิดต่างๆในสารละลายA,BและCในน้ำ เป็นดังนี้สารละลายในน้ำ   ตัวถูกละลาย ความเข้มข้นA               NaCl            58.5g/dm3B                Na2SO4      71g/dm3C                NaOH         10%โดยมวลต่อปริมาตรการเรียงลำดับความเข้มข้นของสารละลายในหน่วย mol/dm3 จากมากไปน้อยข้อใดถูกต้อง(ENT’34)

• A.

A>B>C

• B.

B>A>C

• C.

C>B>A

• D.

C>A>B

D. C>A>B
Explanation
The correct answer is C>A>B. This is because the question asks for the correct order of concentration of the solutes in the solutions A, B, and C. According to the given information, solution C has a concentration of 10% NaOH by mass per volume, which is the highest concentration among the three solutions. Solution A has a concentration of NaCl at 58.5 g/dm3, which is higher than the concentration of Na2SO4 in solution B at 71 g/dm3. Therefore, the correct order of concentration from highest to lowest is C>A>B.

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• 5.

### 5.ของเหลวขนิดหนึ่งมีสูตรเป็นA3B มีความถ่วงจำเพาะ1.50 (มวลอะตอมของA=33,B=21)เมื่อนำA3B  20 cm3 ผสมกับน้ำให้มีปริมาตรสุดท้ายเท่ากับ500cm3 สารละลายที่ได้จะมีความเข้มข้นกี่mol/dm3(ENT’26)

• A.

2.0

• B.

1.5

• C.

1.0

• D.

0.5

D. 0.5
Explanation
The given question states that a liquid with the formula A3B has a specific gravity of 1.50, with the atomic masses of A and B being 33 and 21 respectively. When 20 cm3 of A3B is mixed with water to a final volume of 500 cm3, the resulting solution will have a concentration of how many mol/dm3.

To find the concentration, we need to calculate the number of moles of A3B in the solution. The specific gravity of 1.50 indicates that the density of A3B is 1.50 times that of water. Since the volume of A3B is 20 cm3, the mass of A3B is (20 cm3) * (1.50 g/cm3) = 30 g.

The molar mass of A3B is (33 g/mol) * 3 + (21 g/mol) = 150 g/mol. Therefore, the number of moles of A3B is (30 g) / (150 g/mol) = 0.20 mol.

The final volume of the solution is 500 cm3, which is equal to 0.500 dm3.

Therefore, the concentration of the solution is (0.20 mol) / (0.500 dm3) = 0.40 mol/dm3.

Since the answer choices are not provided in the question, we cannot determine the correct answer based on the given information.

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