Molality is a measure of concentration that relates the moles of solute to the kilograms of solvent, it is described by the following equation:

We are given the molality(2.50m) and kilograms of solvent(0.500kg), so we solve for moles of solute from the equation:


To make a 2.50molal NaOH solution would be needed 1.25moles of solute
Answer: 1.25 moles
Answer:
MgSO4.7H2O
Explanation:
Let the formula for the hydrated magnesium sulphate be MgSO4.xH2O
Mass of the hydrated salt (MgSO4.xH2O) = 12.845g
Mass of anhydrous salt (MgSO4) = 6.273g
Mass of water molecule(xH2O) = Mass of the hydrated salt — Mass of anhydrous salt = 12.845 — 6.273 = 6.572g
Now,we can obtain the number of mole of water molecule present in the hydrated salt as follows:
Molar Mass of hydrated salt (MgSO4.xH2O) = 24 + 32 + (16x4) + x(2 + 16) = 24 + 32 + 64 + x(18) = 120 + 18x
Mass of xH2O/ Molar Mass of MgSO4.xH2O = Mass of water / mass of hydrated salt
18x/120 + 18x = 6.572/12.845
Cross multiply to express in linear form
18x x 12.845 = 6.572(120 + 18x)
231.21x = 788.64 + 118.296x
Collect like terms
231.21x — 118.296x = 788.64
112.914x = 788.64
Divide both side by 112.914
x = 788.64 /112.914
x = 7
Therefore the formula for the hydrated salt (MgSO4.xH2O) is MgSO4.7H2O
D. microwaves, Ultraviolet, x-rays
Answer:
462g
Explanation:
First, let us calculate the molar mass of Cu(CN)2. This is illustrated below:
Molar Mass of Cu(CN)2 = 63.5 + 2(12+14) = 63.5 + 2(26) = 63.5 + 52 = 115.5g/mol
Number of mole of Cu(CN)2 given from the question = 4moles
Mass = number of mole x molar Mass
Mass of Cu(CN)2 = 4 x 115.5
Mass of Cu(CN)2 = 462g