Answer:
A.'C
Explanation:
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We will get the molality from this formula:
Molality = no.of moles of solute / Kg of solvent
So first we need the no.of moles of KNO3 = the mass of KNO3 / molar mass of KNO3
no.of moles of KNO3 = 175 / 101.01 = 1.73 mol
By substitution in the molality formula:
∴ molality = 1.73 / (750/1000) = 2.3 Molal
The mass number of an isotope can be expressed <span>by simply writing the name of the element or symbol followed by a hyphen and the mass number.
Example:
Carbon-13, Carbon-14
Oxygen-17
Uranium-235
</span>
Answer:
The percentage by mass of element X is 25 %.
The percentage by mass of element Y is 75 %
Explanation:
X + Y ⇒ XY
3.5 g of element X + 10.5 g of element Y = 14g in total
⇒Element X : 3.5g / 14g = 0.25 ⇒ x 100 % = 25 %
⇒Element Y : 10.5 / 14 = 0.75 ⇒ x 100 % = 75 %
The percentage by mass of element X is 25 %.
The percentage by mass of element Y is 75 %
