Question

question 1
1 pts
what is the law that ensures that chemical reactions are balanced?
○ law of definite composition
○ first law of thermodynamics
○ the law of conservation of energy
○ the law of conservation of matter
question 2
1 pts
balance the following chemical equation and give the coefficients:
c₂h₄ + o₂ → co₂ + h₂o
○ 1, 3, 2, 2
○ 2, 2, 1, 2
○ 1, 2, 1, 2
○ 2, 3, 1, 3

Explanation:

Question 1

• The law of conservation of matter (mass) states that matter is neither created nor destroyed in a chemical reaction, so chemical equations must be balanced to reflect this (same number of each atom on both sides).
• Law of definite composition: relates to compound composition, not balancing.
• First law of thermodynamics/law of conservation of energy: relate to energy, not matter balancing in reactions.

Step1: Balance Carbon atoms

In \( C_2H_4 \), there are 2 C atoms. So \( CO_2 \) needs a coefficient of 2 to balance C (since each \( CO_2 \) has 1 C). So \( CO_2 \) coefficient is 2.

Step2: Balance Hydrogen atoms

In \( C_2H_4 \), there are 4 H atoms. Each \( H_2O \) has 2 H, so \( H_2O \) coefficient is \( \frac{4}{2}=2 \).

Step3: Balance Oxygen atoms

On the right, \( 2CO_2 \) has \( 2\times2 = 4 \) O, and \( 2H_2O \) has \( 2\times1 = 2 \) O, total O is \( 4 + 2 = 6 \). Each \( O_2 \) has 2 O, so \( O_2 \) coefficient is \( \frac{6}{2}=3 \).

Step4: Check \( C_2H_4 \) coefficient

\( C_2H_4 \) coefficient remains 1 (since we balanced around it). So coefficients are 1 ( \( C_2H_4 \) ), 3 ( \( O_2 \) ), 2 ( \( CO_2 \) ), 2 ( \( H_2O \) ).

Answer:

D. The law of conservation of matter

Question 2