1. solid
2. liquid
3. gas
4. solution
4.Solution
Mixtures are materials composed of two or more kinds of substances that still possess their original properties. Mixtures can also be said to represent a combination of several substances, elements or compounds
There are two types of mixtures, i.e., homogeneous mixture (or solution) and heterogeneous mixture.
The solution is a homogeneous mixture of two or more substances that dissolve one another and each of the constituent substances cannot be distinguished physically anymore.
In chemistry, we already know the phase of matter or state of matter, i.e., solid (s), liquid (l), gas (g), and aqueous (aq). Every chemical solution in a reaction is labeled as an aqueous phase, e.g, as a salt solution.
Consider the following examples:
Keywords: which must be, a mixture of substances, solid, liquid, gas, solution, homogeneous, heterogeneous, phase of matter, state, aqueous, salt, water
the Law of Universal Gravitation
the Law of Stellar Evolution
the Law of Propulsion
B. exothermic.
C. spontaneous.
D. endothermic.
Answer:
The % yield of the reaction is 73.8 %
Explanation:
To solve this, we list out the given variables thus
Mass of aluminium in the experiment = 2.5 g
mass of oxygen gas in the experiment = 2.5 g
Molar mass of aluminium = 26.98 g/mol
molar mass of oxygen O₂ = 32 g/mol
The reaction between aluminium and gaseous oxygen can be written as follows
4Al + 3O₂ → 2Al₂O₃
Thus four moles of aluminium forms two moles of aluminium oxide
Thus (2.5 g)÷(26.98 g/mol) = 0.093 mole of aluminium and
(2.5 g)÷(32 g/mol) = 0.078125 moles of oxygen
However four moles of aluminium react with three moles of oxygen gas O₂
1 mole of aluminum will react with 3/4 moles of oxygen O₂ and 0.093 mole of aluminium will react with 0.093*3/4 moles of O₂ = 0.0695 moles of Oxygen hence aluminium is the limiting reagent and we have
1 mole of oxygen will react with 4/3 mole of aluminium
∴ 0.078125 mole of oxygen will react with 0.104 moles of aluminium
Therefore 0.093 mole of aluminium will react with O₂ to produce 2/4×0.093 or 0.0465 moles of 2Al₂O₃
The molar mass of 2Al₂O₃ = 101.96 g/mol
Hence the mass of 0.0465 moles = number of moles × (molar mass)
= 0.0465 moles × 101.96 g/mol = 4.74 g
The of aluminium oxide Al₂O₃ is 4.74 g, but the actual yield = 3.5 g
Therefore the Percentage yield = ×100 = × 100 = 73.8 % yield
B. 1.3
C. 5.0
D. 7.5 2. Water can act as both an acid and a base in an ionization reaction to form H+ and OH- ions. What is this phenomenon called?
A. neutralization
B. acid dissociation
C. base dissociation
D. self-ionization 3. A solution of vinegar and water has a pH of 6.2. What type of solution is this?
A. acidic
B. basic
C. neutral 4. Hydrochloric acid (HCl) and acetic acid (HC2H3O2) are both acids. HCl completely dissociates in water, while HC2H3O2 does not. Which of the following statements best describes these two acids?
A. HCl is a strong acid; HC2H3O2 is a strong acid.
B. HCl is a weak acid; HC2H3O2 is a weak acid.
C. HCl is a strong acid; HC2H3O2 is a weak acid.
D. HCl is a weak acid; HC2H3O2 is a strong acid.
5. Pyridine is a weak base with the formula C5H5N. Pyridine reacts with water according to the following equation: C5H5N + H2O ---> C5H5NH+ + OH-. What is the formula for the dissociation constant for this base?
A. Kb = [OH-][C5H5NH+]/[C5H5N]
B. Kb = [H+][CO2H-]/[C5H5N]
C. Kb = [C5H5N]/[OH-][CO2H-]
D. Kb = [C5H5N][CO2H-]/[OH-]
Answer: 1. B. 1.3
2. D. self-ionization
3. A. acidic
4. HCl is a weak acid; is a weak acid.
5. A.
Explanation:
1. pH is the negative logarithm of hydrogen ion concentration.
Given:
2. An acid is a substance which donates ions when dissolved in water.
A base is a substance which donates ions when dissolved in water.
Thus as water ionizes to give both ions, it acts as both acid and base.
which is called as self ionization.
3. pH is the measure of acidity or alkalinity of a solution. \Acids have pH less than 7, neutral solutions have pH of 7 and basic solutions have pH more than 7.
As the given solution has a pH of 6.8 which is less than 7, it is an acidic solution.
4. Strong acids are those acids which undergo complete dissociation when dissolved in water.
Weak acids are those acids which do not undergo complete dissociation when dissolved in water.
5. Dissociation constant is the ratio of product of concentration of products to the product of concentration of reactants each raised to their stochiometric coefficients.
The concentration of water is ignored as it is in large excess and thus does not effect the dissociation of pyridine.