Mass = mass/molar mass of ch3ch2nh2
the molar mass of CH3CH2NH2 = 12 +(1x3)+12+(1 x2)+14+(1x2) =45 g/mol
moles is therefore = 1.50g /45g/mol = 0.033 moles
Concentration is the number of moles of solute in a fixed volume of solution
Concentration(c) = number of moles of solute(n) / volume of solution (v)
25.0 mL of water is added to 125 mL of a 0.150 M LiOH solution and solution becomes more diluted.
original solution molarity - 0.150 M
number of moles of LiOH in 1 L - 0.150 mol
number of LiOH moles in 0.125 L - 0.150 mol/ L x 0.125 L = 0.01875 mol
when 25.0 mL is added the number of moles of LiOH will remain constant but volume of the solution increases
new volume - 125 mL + 25 mL = 150 mL
therefore new molarity is
c = 0.01875 mol / 0.150 L = 0.125 M
answer is 0.125 M
To separate some ethanol from water, Jane needs to use the method of simple distillation.
Simple distillation is a separation method in which two liquids can be separated from each other based on differences in boiling point.
Since water has a higher boiling point than ethanol, ethanol is collected first as the distillation proceeds.
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ΔS =S(products) -S(reactants)
Where ΔS is the change of entropy in a reactions
a. ΔS = (2) - (2+1) = -1
b. ΔS = (1+1) -(1) = 1
c. ΔS = (1+2) - (1) = 2
d. ΔS = (2) - (2+1) = -1
e. ΔS = (1) - (1) = 0
ΔS is negative for reaction a. and d.
Given reaction represents dissociation of bromine gas to form bromine atoms
Br2(g) ↔ 2Br(g)
The enthalpy of the above reaction is given as:
ΔH = ∑n(products)Δ
- ∑n(reactants)Δ
where n = number of moles
Δ
= enthalpy of formation
ΔH = [2*ΔH(Br(g)) - ΔH(Br2(g))] = 2*111.9 - 30.9 = 192.9 kJ/mol
Thus, enthalpy of dissociation is the bond energy of Br-Br = 192.9 kJ/mol