3, What is the name for Ni(NO2)3? what is the empirical formula for a compound composed of 2.1%H, 52.8% As and 45.1% O? What volume of liquid X is required to make 65 mL of 0.785M solution of X? (The molar mass of X is 60.5 g/mol, and the density of X is 1.23 g/mL.) 5. If the ΔΗ.xn for the balanced reaction shown in problem #1 is-325 k], how much heat energy (k)) is released when 25.0 g of C4Hio is reacted?
The Correct Answer and Explanation is :
Let’s break down the questions one by one:
1. Name of Ni(NO2)3
This compound consists of nickel (Ni) and the nitrate ion (NO2). The charge on the nitrate ion is typically -1, and since there are three nitrate ions, the nickel ion must have a +3 charge to balance out the charges. Therefore, the name of Ni(NO2)3 is Nickel(III) nitrate.
2. Empirical formula for a compound composed of 2.1% H, 52.8% As, and 45.1% O
To find the empirical formula, we’ll convert the percentage composition to moles:
- Hydrogen (H):
( \frac{2.1 \, \text{g}}{1.008 \, \text{g/mol}} = 2.08 \, \text{mol} ) - Arsenic (As):
( \frac{52.8 \, \text{g}}{74.92 \, \text{g/mol}} = 0.705 \, \text{mol} ) - Oxygen (O):
( \frac{45.1 \, \text{g}}{16.00 \, \text{g/mol}} = 2.82 \, \text{mol} )
Now, divide each mole value by the smallest number of moles, which is 0.705:
- H: ( \frac{2.08}{0.705} = 2.95 \approx 3 )
- As: ( \frac{0.705}{0.705} = 1 )
- O: ( \frac{2.82}{0.705} = 4.00 )
The empirical formula is AsH3O4.
3. Volume of liquid X required to make 65 mL of 0.785M solution
We need to use the formula for molarity:
[ M = \frac{\text{moles of solute}}{\text{volume of solution (L)}} ]
First, calculate the number of moles required:
[ 0.785 \, \text{mol/L} \times 0.065 \, \text{L} = 0.051025 \, \text{mol} ]
Now, find the mass of liquid X required:
[ \text{mass} = 0.051025 \, \text{mol} \times 60.5 \, \text{g/mol} = 3.087 \, \text{g} ]
Finally, use the density to find the volume:
[ \text{Volume} = \frac{\text{mass}}{\text{density}} = \frac{3.087 \, \text{g}}{1.23 \, \text{g/mL}} = 2.51 \, \text{mL} ]
So, 2.51 mL of liquid X is required.
4. Heat energy released when 25.0 g of C4H10 is reacted
Given the enthalpy change (ΔH) is -325 kJ for the balanced reaction, and the mass of C4H10 is 25.0 g, first, calculate the moles of C4H10:
[ \text{Molar mass of C4H10} = (4 \times 12.01) + (10 \times 1.008) = 58.12 \, \text{g/mol} ]
[ \text{moles of C4H10} = \frac{25.0 \, \text{g}}{58.12 \, \text{g/mol}} = 0.430 \, \text{mol} ]
Now, use the enthalpy change per mole to find the total heat energy released:
[ \text{heat energy} = \text{moles of C4H10} \times \Delta H = 0.430 \, \text{mol} \times (-325 \, \text{kJ/mol}) = -139.75 \, \text{kJ} ]
Thus, -139.75 kJ of heat energy is released.
5. Explanation
- Nickel(III) nitrate (Ni(NO2)3) is formed because the nickel ion must have a +3 charge to balance the three -1 charges from the nitrate ions.
- The empirical formula of a compound tells you the simplest ratio of atoms present. By converting percentages to moles and simplifying, we find that the empirical formula of the compound is AsH3O4, meaning the ratio of arsenic to hydrogen to oxygen atoms is 1:3:4.
- The volume calculation for liquid X involves first determining how many moles are needed for the desired concentration and then finding the corresponding volume based on the molar mass and density. This shows how solutions are prepared by accurately measuring both mass and volume.
- The heat energy calculation is a straightforward use of the enthalpy change, where knowing the amount of reactant (C4H10) helps us determine the total heat released based on the reaction’s enthalpy.
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