What are exercises on calculating molecular mass for grade 8 students in Vietnam (from basic to advanced)? What are evaluation formats trực tiếp bóng đá euro hôm nay Natural Sciences subject for grade 8 in Vietnam?
What are exercises on calculating molecular mass for grade 8 students in Vietnam (from basic to advanced)?
Molecular mass or molecular weight is the total mass trực tiếp bóng đá euro hôm nay all the atoms that make up a molecule.
In the grade 8 natural science subject, there are two main types trực tiếp bóng đá euro hôm nay exercises on calculating molecular mass as follows:
Type 1:Identify the chemical element's name based on atomic mass
Given that element X has an atomic mass that is 3.5 times the atomic mass trực tiếp bóng đá euro hôm nay oxygen. Identify the name and chemical symbol trực tiếp bóng đá euro hôm nay element X.
Guidance:
Expressing X having an atomic mass that is 3.5 times the atomic mass trực tiếp bóng đá euro hôm nay oxygen: X = 3.5.O
The atomic mass trực tiếp bóng đá euro hôm nay O is known → find the atomic mass trực tiếp bóng đá euro hôm nay X → refer to the table to determine the name trực tiếp bóng đá euro hôm nay element X → chemical symbol
Solution:
X = 3.5 . O = 3.5 . 16 = 56
= X is the element iron, chemical symbol Fe.
Type 2:Find the name trực tiếp bóng đá euro hôm nay element X, chemical symbol when knowing the molecular weight
A compound consists trực tiếp bóng đá euro hôm nay 1 atom trực tiếp bóng đá euro hôm nay X bonded to 2 atoms trực tiếp bóng đá euro hôm nay oxygen and is 22 times heavier than the hydrogen molecule.
a/ Calculate the molecular weight trực tiếp bóng đá euro hôm nay the compound.
b/ Calculate the atomic mass trực tiếp bóng đá euro hôm nay X, provide the name and chemical symbol
Guidance
The hydrogen molecule (2H) = Molecular weight = 2 . 1 = 2
The compound is 22 times heavier than the hydrogen molecule = Molecular weight trực tiếp bóng đá euro hôm nay the compound: 2.22 = 44
1 atom trực tiếp bóng đá euro hôm nay X is bonded to 2 atoms trực tiếp bóng đá euro hôm nay oxygen = compound (1X; 2O) = Molecular weight = X + 2.16 = X + 32
= X + 32 = 2 . 22 = 44
= X = 44 – 32 = 12
Thus, X is the element carbon, chemical symbol is C.
Students can refer to followingmolecular mass calculation exercises.
| Question 1: The molecular mass trực tiếp bóng đá euro hôm nay Cl2 is A. 35.5 amu. B. 36.5 amu. C. 71 amu. D. 73 amu. Answer: C Question 2: The molecular mass trực tiếp bóng đá euro hôm nay HCl is A. 35.5 amu. B. 36.5 amu. C. 71 amu. D. 73 amu. Answer: B Question 3: The molecular mass trực tiếp bóng đá euro hôm nay CH4, Mg(OH)2, KCl respectively is A. 16 amu, 74.5 amu, 58 amu B. 74.5 amu, 58 amu, 16 amu C. 17 amu, 58 amu, 74.5 amu D. 16 amu, 58 amu, 74.5 amu Answer: D Question 4: Write the molecular formula and calculate the molecular mass trực tiếp bóng đá euro hôm nay a compound with 1 atom trực tiếp bóng đá euro hôm nay Na, 1 atom trực tiếp bóng đá euro hôm nay N, and 3 atoms trực tiếp bóng đá euro hôm nay oxygen in the molecule A. NaNO3, molecular mass is 85 B. NaNO3, molecular mass is 86 C. NaN3O, molecular mass is 100 D. No compound satisfies Answer: A Question 5: Choose the incorrect answer A. The molecular formula trực tiếp bóng đá euro hôm nay a monatomic substance only includes the chemical symbol trực tiếp bóng đá euro hôm nay one element B. Sulfur has the chemical formula S C. The molecular mass trực tiếp bóng đá euro hôm nay CaCO3 is 100 amu D. All answers are incorrect Answer: A Question 6: The molecular mass trực tiếp bóng đá euro hôm nay H2SO4 is: A. 9 amu. B. 50 amu. C. 96 amu. D. 98 amu. Answer: D Question 7: The mass trực tiếp bóng đá euro hôm nay H2SO4 in a molecule is A. 49 grams B. 98 grams C. 49 amu D. 98 amu Answer: D Question 8: The molecular mass trực tiếp bóng đá euro hôm nay the compound Fe(OH)3 is A. 107 amu. B. 107 grams. C. 73 amu. D. 73 grams. Answer: A Question 9: The molecular mass trực tiếp bóng đá euro hôm nay the compound N2O5 is: A. 30 amu B. 44 amu C. 108 amu D. 94 amu Answer: C Question 10: The molecular mass trực tiếp bóng đá euro hôm nay CH4, Mg(OH)2, KCl respectively is A. 16 amu, 74.5 amu, 58 amu B. 74.5 amu, 58 amu, 16 amu C. 17 amu, 58 amu, 74.5 amu D. 16 amu, 58 amu, 74.5 amu Answer: D Question 11: Substances with the same molecular mass are (given that O = 16, N = 14, S = 32, C = 12) A. O3 and N2 B. CO and N2 C. SO2 and O2 D. NO2 and SO2 The answer to be selected is: B Question 12: Choose the incorrect answer A. The molecular formula trực tiếp bóng đá euro hôm nay a monatomic substance only includes the chemical symbol trực tiếp bóng đá euro hôm nay one element B. Sulfur has the chemical formula S C. The molecular mass trực tiếp bóng đá euro hôm nay CaCO3 is 100 amu D. All answers are incorrect Answer: A Question 13: From the chemical formula trực tiếp bóng đá euro hôm nay CuSO4, what can be inferred? A. CuSO4 is composed trực tiếp bóng đá euro hôm nay 3 elements Cu, O, S. B. There are 4 oxygen atoms in the molecule. C. The molecular mass is 160 amu. D. All answers. Answer: D Question 14: Methane, the main component trực tiếp bóng đá euro hôm nay natural gas, has the molecular formula CH4. The molecular mass trực tiếp bóng đá euro hôm nay this compound is A. 14 amu. B. 15 amu. C. 16 amu. D. 17 amu. Question 15: Table sugar has the chemical formula C12H22O11. The molecular mass trực tiếp bóng đá euro hôm nay table sugar is A. 180 amu. B. 162 amu. C. 342 amu. D. 108 amu. |
Note: These exercisesare for reference only!
What are exercises on calculating molecular mass for grade 8 students in Vietnam (from basic to advanced)? What are evaluation formats trực tiếp bóng đá euro hôm nay Natural Sciences subject for grade 8 in Vietnam? (Image from the Internet)
What are evaluation formats trực tiếp bóng đá euro hôm nay Natural Sciences subject for grade 8 in Vietnam?
According to clause 3 Article 5 trực tiếp bóng đá euro hôm nayCircular 22/2021/TT-BGDDT:
Evaluation Method
...
- Evaluation format for the subjects
a) Evaluating by comments for the subjects: Physical education, Arts, Music, Fine Arts, Local education content, Experiential activities, career orientation; study results by subjects are evaluated by comments at one trực tiếp bóng đá euro hôm nay two levels: Achieved, Not achieved.
b) Evaluating by comments combined with scoring for the subjects in the general education program, except for the subjects specified at point a trực tiếp bóng đá euro hôm nay this clause; study results by subjects are evaluated with scores on a scale trực tiếp bóng đá euro hôm nay 10, if using a different scale, it must be converted to the scale trực tiếp bóng đá euro hôm nay 10. Scores are whole numbers or decimal numbers rounded to the first decimal place.
Thus, the grade 8 natural science subject is evaluated by comments combined with scoring.
What are requirements for evaluating the study results trực tiếp bóng đá euro hôm nay grade 8 Natural Science in Vietnam?
Based on Article 4 trực tiếp bóng đá euro hôm nayCircular 22/2021/TT-BGDDT, the evaluation trực tiếp bóng đá euro hôm nay grade 8 natural science must meet the following requirements:
- Evaluate based on the achievements required by the general education program.
- Ensure that the evaluation is accurate, comprehensive, fair, honest, and objective.
- Evaluate using various methods, formats, techniques, and tools; combine regular assessment and periodic assessment.
- Evaluate for the progress trực tiếp bóng đá euro hôm nay students; emphasize encouragement and motivation trực tiếp bóng đá euro hôm nay students' effort in practice and study; do not compare students with each other.
