32. A fictional element has two isotopes, each making up 50% of the population.

Question

32. A fictional element has two isotopes, each making up 50% of the population. Isotope 1 has a mass of 60.0 amu, Isotope 2 has a mass of 63.0 amu. Calculate the atomic mass of the fictional element. 33. Increasing the intermolecular forces of a liquid will have what effects on its viscosity, evaporation rate, surface tension and vapor pressure? 34. When sufficient quantity of heat has been added to reach the boiling point of a solution, what happens to any additional heat added while the liquid is boiling? 35. What is the theoretical yield of CaCI2 in grams if we start with 3 moles of HCI and 1.0 moles of Ca(OH)2? Reaction: 2HCl + Ca(OH)2 right arrow 2H2O + CaCl2, 36. What is the volume of 29.5 g of nitrogen gas at STP?

Explanation / Answer

32.

A1( atomic mass of 1st isotope) = 60 amu

X1(Percentage composition of isotope 1) = 50%

A2 ( Atomic mass of 2nd isotope) = 63 amu

X2 (Percentage composition of isotope 2 ) = 50%

Average atomic mass of element(A) = (A1*X1 + A2*X2) / (X1+X2)

A = (60 * 50 + 63*50) / (50+50)

A = 61.50 amu

33.

Viscosity of liquid will increase on increasing the intermolecular forces of a liquid because on increasing intermolecular forces of a liquid the substance is able to flow more easily

As the intermolecular forces of liquid increases the molecules are more tightl bound so the rate of evaporation decreases.

As the intermolecular forces of liquid increases the toughness of the liquid surface increases hence the surface tension increases

As the intermolecular forces of liquid increases there will be little amount of gas above the liquid because of which the vapour pressure decreases.

34.

When sufficient quantity of heat is added to reach the boiling point of solution then the additional heat is required to change the state of the liquid. That is after heating water upto 100 degreeC the additional heat is used to change the state of water into vapor . This additional heat required to change the state of liquid into vapour is called Latent heat of vaporization.

35.

2HCl + Ca(OH)2 -------> 2H2O + CaCl2

2 mol of HCl gives 1 mol of CaCl2

And 1 mol of Ca(OH)2 gives 1 mol of CaCl2

But moles of HCl available is 3 mol but we require only 2 mol so 1 mol is extra.

Moles of Ca(OH)2 available is 1 mol and only 1 mol is required So Ca(OH)2 is present in limited quantity hence Ca(OH)2 is the limiting reagent.

1 mol of Ca(OH)2 gives 1 mol of CaCl2

So,

mass of CaCl2 = moles * molar mass

mass of CaCl2 = 1 mol * 111 g/mol = 111 g

So,

theoretical yield of CaCl2 = 111 g

36.

moles of N2 gas = given mass / molar mass

moles of N2 gas = 29.5 g / 28 g/mol

moles of N2 gas = 1.053 mol

Now,

moles of N2 = given volume / molar volume at STP

1.053 mol = V / 22.4 L

V = 23.6 L

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