Question 1 : A fictional element has two isotopes and a molar mass of 82.56 g/mo

Question

Question 1 :
A fictional element has two isotopes and a molar mass of 82.56 g/mol. The first isotope has an atomic mass of 81.06 u and 27.33 % of the element's atoms are this isotope. What is the atomic mass (in u) of the second isotope?

Question 2 :

What mass (in g) of butanol (C4H10O) is required such that its combustion produces 55.6 g of products? The combustion of a compound (containing C, H, and O) is its reaction with molecular oxygen (O2) to produce water and carbon dioxide.

Question 3 :

322.8 g of SO2(g), 426.5 g of CaCO3(s), and 119.7 g of O2(g) react in the following fashion:
2 SO2(g) + 2 CaCO3(s) + O2(g) ---> 2 CaSO4(s) + 2 CO2(g)

What mass (in g) of CaSO4(s) can be produced?

Question 4 :
We have a container enclosing a mixture of N2(g) and O2(g). The total pressure is 4.01 atm. The temperature is 25.00 oC and the volume of the container is 19.0 L. If the mass of N2 in the container is 37.1 g, what is the partial pressure of O2 (in atm) within the container?
Question 5 :

The density of a sample of NH3(g) at a pressure of 1.00 atm is 0.842 g/L. What is the root-mean-square speed (in m/s) of the molecules in this sample?
Question 6 :

In a 5.00 L steel container at 575 K, the partial pressures of H2(g) and O2(g) are respectively 20.04 and 14.98 atm. The H2(g) and the O2(g) react together to produce H2O(g). The final temperature remains at 575 K and the volume remains at 5.00 L. What is the final total pressure (in atm)?

Question 7 :
We have a bomb calorimeter with a heat capacity of 555 J/K. In this bomb calorimeter, we place 1000.0 mL of water. We burn 2.565 g of a solid in this bomb calorimeter. The temperature of the bomb calorimeter and the water increases by 2.24 oC. The molar mass of the solid is 588.9 g/mol. How much heat (in kJ) will be released if we were to burn 0.137 mol of this same solid in the bomb calorimeter? Keep in mind that we want to find the amout of heat released. The specific heat capacity or water is 4.184 J/K/g. Approximate the density of water as being exactly 1.00 g/mL.
Question 8 :

The standard enthalpies of formation, at 25.00 oC, of methane (CH4(g)), water (H2O(l)), and carbon dioxide (CO2(g)) are, respectively, -74.6 kJ/mol, -285.8 kJ/mol, and -393.5 kJ/mol. Calculate the amount of heat released (in kJ) during the combustion of 18.04 L of methane under a constant pressure of 1.000 atm at 25.00 oC (N.B. combustion is the reaction with molecular oxygen to produce water and carbon dioxide.)

Question 9 :

We place a metal rod weighing 5.00 g with a specific heat capacity of 0.432 J/K/g in 24.9 mL of water. The specific heat capacity of water is 4.184 J/K/g and we make the approximation that its density is exactly 1.000 g/mL. The water has an initial temperature of 20.0 oC and the metal rod has an initial temperature of 85.2 oC. What is the final temperature (in oC) of the water and metal rod?

Explanation / Answer

1.

Average atomic mass = (1st Isotopic mass * percent abundance /100) + (2nd isotopic mass * percent abundance /100)

82.56 = (81.06 * 0.2733) + (m * ( 1- 0.2733))

m * (0.7267) = 82.56 - ( 81.06 * 0.2733)

m = 60.4 / 0.7267

m = mass of second isotope = 83.12 g.

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