as additional KNO3(s) is added to a saturated solution of KNO3 at constant temperature, the concentration of the solution? (I know it remains the same but why??)
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The number of moles in 987 grams of Ra(OH)2 = 3.8 moles
Calculating number of moles
Ra = 226g
O= 16g
H = 1
Therefore molar mass of Ra(OH)2= 226+ (16+1)×2
= 260g/mol
The molar mass of Ra(OH)2 = 260g/mol
Thus means that 260g of Ra(OH)2 makes up 1 mole
Therefore, 987 g = X moles
Make X moles the subject of formula,
X mole = 987/260
= 3.8 moles
Therefore, the number of moles in 987 grams of Ra(OH)2 = 3.8 moles
Learn more about molar mass here:
Answer : 3.79 moles are in 987 grams of .
Solution : Given,
Mass of = 987 g
Molar mass of = 260 g/mole
Now we have to calculate the moles of .
Formula used :
Now put all the given values in this formula, we get the moles.
Therefore, 3.79 moles are in 987 grams of .
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The question is incomplete, this is the complete question;
In the process of attempting to characterize a substance, a chemist makes the following observations. Which are physical properties and which are chemical properties?
(a) The substance is a silvery white, lustrous metal.
(b) The substance melts at 649 ∘C
(c) The substance boils at 1105 ∘C.
(d) The density of the substance at 20 ∘C is 1.738 g/cm³.
(e) The substance burns in air, producing an intense white light.
(f) The substance reacts with chlorine to give a brittle white solid.
(g) The substance can be pounded into thin sheets or drawn into wires.
(h) The substance is a good conductor of electricity.
Answer:
(a) Physical
(b) Physical
(c) Physical
(d) Physical
(e) Chemical
(f) Chemical
(g) Physical
(h) Physical
Explanation:
(a) The substance is a silvery white, lustrous metal - is appearance which is physical.
(b) The substance melts at 649 ∘C metling point is a physical measurement
(c) The substance boils at 1105 ∘C boiling point is a physical measurement
(d) The density of the substance at 20 ∘C is 1.738 g/cm3 how heavy a substance is,is physical.
(e) The substance burns in air, producing an intense white light. Burning is a chemical change. It is a reaction of a substance with oxygen
(f) The substance reacts with chlorine to give a brittle white solid. This is a chemical reaction as the question says.
(g) The substance can be pounded into thin sheets or drawn into wires. Ductility is a physical change, the substance remains chemically unchanged
(h) The substance is a good conductor of electricity. Any conductivity is physical, the substance remains chemically unchanged
Final answer:
The substance in question is likely a pure metal, more specifically Magnesium, because of its documented properties such as lustrous appearance, ability to be drawn into wires, and high electrical conductivity. Its properties like high melting and boiling points and its reactions suggest it could be from Group 1, but its ability to be formed into sheets and wires and its high conductivity suggest it's not an ionic compound like sodium chloride.
Explanation:
The substance described in the question seems to be an example of pure metal due to the properties like lustrous appearance, ability to be drawn into wires or pounded into sheets, and high conductivity of electricity. However, some of the properties like reaction with chlorine, production of intense white light upon burning in air, and its high melting and boiling points suggest that it could be a Group 1 element such as sodium or potassium, which are known for these characteristics. Coupled with information of its density and its ability to form brittle white solid upon reaction with chlorine, it seems to likely be Magnesium, a silvery-white lustrous metal.
Furthermore, ionic compounds like sodium chloride have high melting and boiling points, conduct electricity when molten, and ions are freed to move allowing conductivity. However, such compounds, unlike pure metals, cannot be drawn into wires or pounded into sheets and are usually brittle solids, which would make it less likely that the substance in question is an ionic compound.
The most confident identification will be based on the substance's observed physical and chemical properties and their comparison to known properties of pure metals and ionic compounds.
Learn more about Identifying Substances here:
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