A student is given two clear solutions. One solution contained lead ions, Pb2+ and the other solution contains chloride ions, Cl
2 answers:
Answer: A chemical change has occurred.
Explanation: A chemical change is a change which results when there is a change in the chemical composition of the atoms.
Chemical changes are accompanied by:
a) Change in color
b) Absorption or release of heat
c) formation of precipitates
d) production of gas
The white powder is precipitates of lead chloride which do not dissolve.
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Answer:
Enthalpy of formation = -947.68KJ/mol
Explanation:
Enthalpy of formation is the heat change when one mole of a substance is formed from its element in its standard states and in standard conditions of temperature and pressure. it may be positive or negative, if positive, it is an endothermic reaction where the heat content of the product is greater than that of the reactants, and if negative, it is exothermic reaction - where the heat content of the reactants is greater than the products. the enthalpy of formation is measured in KiloJoule/Moles (KJ/Mole).
From the value of the enthalpy of formation of NaHCO3, it shows that the reaction is exothermic, that is the formation of NaHCO3 from its constituents elements. As such, the heat content of the reactants is greater than the products.
The step by step explanation is shown in the attachment.
Answer: A volume of 455 mL from 0.550 M KBr solution can be made from 100.0 mL of 2.50 M KBr.
Explanation:
Given: = ?,
= 0.55 M
= 100.0 mL,
= 2.50 M
Formula used to calculate the volume of KBr is as follows.
Substitute the values into above formula as follows.
Thus, we can conclude that a volume of 455 mL from 0.550 M KBr solution can be made from 100.0 mL of 2.50 M KBr.