<u>Answer:</u> The mass percent of lead in lead (IV) carbonate is 63.32 %
<u>Explanation:</u>
The given chemical formula of lead (IV) carbonate is 
To calculate the mass percentage of lead in lead (IV) carbonate, we use the equation:

Mass of lead = (1 × 207.2) = 207.2 g
Mass of lead (IV) carbonate = [(1 × 207.2) + (2 × 12) + (6 × 16)] = 327.2 g
Putting values in above equation, we get:

Hence, the mass percent of lead in lead (IV) carbonate is 63.32 %
Answer: 1709.4 Joules
Explanation:
The quantity of Heat Energy (Q) released on cooling a heated substance depends on its Mass (M), specific heat capacity (C) and change in temperature (Φ)
Thus, Q = MCΦ
Since Q = ?
M = 18.5 grams
Recall that the specific heat capacity of copper C = 0.385 J/g.C
Φ = 285°C - 45°C = 240°C
Then, Q = MCΦ
Q = 18.5grams x 0.385 J/g.C x 240°C
Q = 1709.4 Joules
Thus, 1709.4 Joules is released when copper is cooled.
When the concentrations of CO2 and H2CO3 are both horizontal lines then the rate of the forward reaction is the same as the rate of the reverse reaction.
<h3>What is rate of reaction?</h3>
The term rate of reaction refers to how fast or slow a reaction proceeds. Recall that the rate of reaction is measured from the rate of disappearance of reactants or the rate of appearance of products.
When the [CO2] and [H2CO3 ] are both horizontal lines, the rate of the forward reaction is the same as the rate of the reverse reaction.
Let us recall that the reaction is reversible hence addition of H2CO3 will increase the concentration of H2CO3, the reverse reaction would be favored.
Learn more about rate of reaction: brainly.com/question/8592296
Answer:
Iodine is most reactive because it is very close to having a "full shell" which is 8 electrons so they are "eager" to gain the last electron to became balanced, so that makes it the most reactive. Hope that helps:)
Explanation: