It is, Reactants react to produce new substances known as products.
because a chemical reaction is the combining of different reactants
Answer:
If 1000. mL of water freezes, which of the following is a reasonable approximation for the volume of the resulting ice?
Group of answer choices
1000. mL
961 mL
1040 mL
Explanation:
Ice is fewer denser than water.
The reason is the volume occupied by the same mass of ice with water is more than the volume occupied by water. Ice has more empty space within it.
Due to this reason, ice floats on water.
When 1000ml of water freezes to ice then its volume is greater than water.
Among the given options the correct answer is 1040 mL .
11. Atomic number
12. in the nucleus with neutrons
Answer:
A. 0.038 g.
Explanation:
- The decay of carbon-14 is a first order reaction.
- The rate constant of the reaction (k) in a first order reaction = ln (2)/half-life = 0.693/(5730 year) = 1.21 x 10⁻⁴ year⁻¹.
<u><em>The integration law of a first order reaction is:</em></u>
<em>kt = ln [Ao]/[A]</em>
k is the rate constant = 1.21 x 10⁻⁴ year⁻¹.
t is the time = 17,190 years.
[Ao] is the initial concentration of carbon-14 = 0.300 g.
[A] is the remaining concentration of carbon-14 = ??? g.
∵ kt = ln [Ao]/[A]
∴ (1.21 x 10⁻⁴ year⁻¹)(17,190 years) = ln (0.300 g)/[A]
2.08 = ln (0.300 g)/[A]
Taking exponential for both sides:
8.0 = (0.300 g)/[A]
<em>∴ [A] = 0.0375 g ≅ 0.038 g</em>
Answer:
- <u><em>It is positive when the bonds of the product store more energy than those of the reactants.</em></u> (the second statement)
Explanation:
ΔHf is the change of enthalpy during the reaction, which is equal to the sum of enthaply changes of the products less the sum of the enthalpy changes of the reactants.
- ΔHf = ∑ (ΔH products) - ∑ (ΔH reactants)
Also, ΔHrxn, per definition, is the potential chemical energy stored in the bonds of the products less the chemical potential energy stored in the bonds of the reactants.
Then, when the potential chemical energy stored in the bonds of the products is greater than the chemical potential energy stored in the bonds of the reactants ΔHrxn is positive.
Hence, you conclude that ΔHf is positive when the bonds of the product store more energy than those of the reactants (second statement from the choices).
Some brief comments about the other statements:
- The standard enthalpy of formation, ΔHf, is zero for an element in its standard state, not for a compound.
- For a compound the enthalpy of formation at 25ºC and 1 atm (the standard state) may be positive or negative.
- Also, note that the standard state for any element is not liquid: some are solids, some are gases, and some are liquids at 25ºC and 1 atm.
