Answer:
b. 0.22 L
Explanation:
Step 1: Write the balanced equation
4 HNO₃(l) ⇒ 4 NO₂(g) + 2 H₂O(l) + O₂(g)
Step 2: Calculate the moles corresponding to 2.5 g of HNO₃
The molar mass of HNO₃ is 63.01 g/mol.
2.5 g × 1 mol/63.01 g = 0.040 mol
Step 3: Calculate the moles of O₂ produced from 0.040 moles of HNO₃
The molar ratio of HNO₃ to O₂ is 4:1. The moles of O₂ produced are 1/4 × 0.040 mol = 0.010 mol.
Step 4: Calculate the volume corresponding to 0.010 moles of O₂
Assuming the reaction takes place at standard temperature and pressure, the volume of 1 mole of O₂ is 22.4 L.
0.010 mol × 22.4L/1 mol = 0.22 L
Answer:
Choice number two. The value of "X" in this equation should be constant for all elements across a period.
Explanation:
Electrons are negative while protons are positive. Electrons are attracted to the proton but repel each other.
Consider an atom where electrons occupy more than one energy level. Consider the Bohr Model for that atom. Protons in the nucleus attract the electrons towards the center of the atom. However, at the same time, electrons in the inner shell will repel the valence electrons. That creates an outward force that pushes the valence electrons away from the atom.
The two forces mostly balance each other, but the attraction is slightly stronger. As a result, the overall force on the valence electrons is attractive. The effective nuclear charge gives the number of protons required to produce an attraction of that strength if there was no repulsion at all.
The value of effective nuclear charge is approximately the same as atomic number minus the number of inner-shell electrons. Apparently, the "X" in this question stands for the number of inner-shell electrons.
By the Aufbau Principle, all spots in the inner shell must be filled before more electrons can be added. Additionally, atoms in the same period have the same number of inner shells. As a result, the number of inner-shell electrons will be the same for all atoms in each period. Hence, the value of "X" should stay (approximately) the same across each period.
This uses the concept of freezing point depression. When faced with this issue, we use the following equation:
ΔT = i·Kf·m
which translates in english to:
Change in freezing point = vant hoff factor * molal freezing point depression constant * molality of solution
Because the freezing point depression is a colligative property, it does not depend on the identity of the molecules, just the number of them.
Now, we know that molality will be constant, and Kf will be constant, so our only unknown is "i", or the van't hoff factor.
The van't hoff factor is the number of atoms that dissociate from each individual molecule. The higher the van't hoff factor, the more depressed the freezing point will be.
NaCl will dissociate into Na+ and Cl-, so it has i = 2
CaCl2 will dissociate into Ca2+ and 2 Cl-, so it has i = 3
AlBr3 will dissociate into Al3+ and 3 Br-, so it has i = 4
Therefore, AlBr3 will lower the freezing point of water the most.
Answer:
because water wets stuff expect for fire.
