1) moles = mass/mR
CaCO3 Mr = 40 + 12 + (16×3)
= 52 + 48
= 100
mass = 15
so the moles would be 15 ÷ 100
which is 0.15 moles of CaCO3
2) moles = mass ÷ Mr
Mr of Al2O3 = 27 + (16×3)
= 27 + 48
= 75
mass = 204
so the moles would be 204/75 which is 2.72 moles of Al2O3
Oil, petroleum
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The vapor pressure of a compound refers to the pressure generated by the vapour of a compound in equilibrium with its condensed stage. The major determinant of a compound vapour pressure is temperature. The vapour pressure of an aqueous solution of sodium chloride will be lower than that of pure water. This is because, dissolution of solute in a solvent always reduces the vapour pressure of the solution as a result of interactions between the molecule of the solute and the solvent. Thus, a pure compound will always have a higher vapour pressure than a solution.
Answer:
A reaction in which the entropy of the system decreases can be spontaneous only if it is exothermic.
Explanation:
The spontaneity of a reaction depends on the Gibbs free energy(ΔG).
- If ΔG < 0, the reaction is spontaneous.
- If ΔG > 0, the reaction is nonspontaneous.
ΔG is related to the enthalpy (ΔH) and the entropy (ΔS) through the following expression:
ΔG = ΔH - T.ΔS
where,
T is the absolute temperature (always positive)
Regarding the exchange of heat:
- If ΔH < 0, the reaction is exothermic.
- If ΔH > 0, the reaction is endothermic.
<em>Which statement is true? </em>
<em>A reaction in which the entropy of the system decreases can be spontaneous only if it is exothermic. </em>TRUE. If ΔS < 0, the term -T.ΔS > 0. ΔG can be negative only if ΔH is negative.
<em>A reaction in which the entropy of the system increases can be spontaneous only if it is endothermic.</em> FALSE. If ΔS > 0, the term -T.ΔS < 0. ΔG can be negative if ΔH is negative.
<em>A reaction in which the entropy of the system decreases can be spontaneous only if it is endothermic.</em> FALSE. If ΔS < 0, the term -T.ΔS > 0. ΔG cannot be negative if ΔH is positive.
<em>A reaction in which the entropy of the system increases can be spontaneous only if it is exothermic.</em> FALSE. If ΔS > 0, the term -T.ΔS < 0. ΔG can be negative even if ΔH is positive, as long as |T.ΔS| > |ΔH|.
Answer:
a fruit and oatmeal bar contains 142000 calories.
A nutritional calorie, or kilocalorie, is equal to 1000 calories.
E = 142 kcal · 1000 cal/kcal.
E = 142 000 cal.
Calorie (cal), or small calorie, is the amount of energy needed to heat one gram of water by one degree Celsius.
One small calorie is approximately 4.2 joules.
A calorie is a unit of energy.
Explanation:
hope it helps :)
