Answer:
Wide melting point range - impure sample with multiple compounds
Experimental melting point is close to literature value - pure sample of a single compound
Experimental melting point is below literature value - impure sample with multiple compounds
Narrow melting point range - pure sample of a single compound
Explanation:
The melting point of substances are easily obtainable from literature such as the CRC Handbook of Physics and Chemistry.
A single pure substance is always observed to melt within a narrow temperature range. This melting temperature is always very close to the melting point recorded in literature for the pure compound.
However, an impure sample with multiple compounds will melt over a wide temperature range. We also have to recall that impurities lower the melting point of a pure substance. Hence, the experimental melting point of an impure sample with multiple compounds is always below the literature value.
The weak ionization constant (Ka)
for HCN is equal to:
Answer:
Ka = [H⁺] × [CN⁻] / [HCN]
Explanation:
Cyanhydric acid is a weak acid, according to the following equation:
HCN(aq) ⇄ H⁺(aq) + CN⁻(aq)
The acid ionization constant (Ka) is equal to the product of the concentrations of the ions raised to the stoichiometric coefficients divided by the concentration of the undissociated acid raised to its stoichiometric coefficient.
Ka for HCN is:
Ka = [H⁺] × [CN⁻] / [HCN]
In the silver recovery lab you will be doing chemical reactions and forming solid ionic compounds from their soluble ions. this question will give you practice in writing ionic compunds. What is chemical formula of the nuetral compound formed from the ions below:
1. Cr3+ ions and Cl- ions
2. Mn4+ ions and O2^- ions
3. Mg2+ ions and CO3^2- ions
Answer:
1. CrCl₃ 2. MnO₂ 3. MgCO₃
Explanation:
For a compound to be neutral, we need the same number of positive charges and negative charges.
1. Cr³⁺ ions and Cl⁻ ions. We will need 1 Cr³⁺ cation and 3 Cl⁻ anions. The chemical formula is CrCl₃.
2. Mn⁴⁺ ions and O²⁻ ions. We will need 1 Mn⁴⁺ cation and 2 O²⁻ anions. The chemical formula is MnO₂.
3. Mg²⁺ ions and CO₃²⁻ ions. We will need 1 Mg²⁺ cation and 1 CO₃²⁻ anion The chemical formula is MgCO₃.
A stain is made up of molecules that do not have charged regions. What soap/solvent combination should I use?Are there multiple?
Answer:
The answer is below
Explanation:
Yes, there are multiple combinations.
Firstly, a solvent or soap combination could be used as a polar solvent with soap. In this way, the nonpolar region of the soap molecules would mix directly with the stain while the solvent would surround the soap-stain micelle.
Secondly, another method or way is to have a combination of a nonpolar solvent with no soap. In this method, however, it is the solvent that would mix directly with the stain.
The compound magnesium nitrate has the formula Mg(NO3)2.
What is the relative formula mass of magnesium nitrate?
Explanation:
Answer
Open in answr app
Correct option is
C
148
1 atom of Mg=1x24=24
2 atom of N=2x14=28
6 atom of O=6x16=96
Total mass=148
Match all the terms that apply to each element. Some terms may apply to more than one element.
a. Main group element
b. halogen
c. noble gas
d. inner transition element
e. alkaline earth
f. Non-metal
g. Alkali metal
h. Metalloid
i. Metal
1. Titanium
2. Gold
3. Argon
4. Thallium
Answer:
Titanium - Metal
Gold - Metal
Argon - noble gas
Thallium - Metal
Explanation:
A metal is a species that easily looses electrons to yield a positive ion. Metals are found in the left hand side of the periodic table.
Thallium is a groups 13 metal, gold is a group 11 metal while titanium is a 4 metal.
However, argon is a noble gas hence it belongs to groups 18 of the periodic table.
Titanium -metal
gold - metal,
Argon - noble gas
Thallium -metal, transition metal
Explanation:
In modern periodic table :
Metals are listed from the middle to left-hand side of the periodic tableNonmetals are listed on the upper right-hand side of the periodic tableMetalloids divide the periodic table in a zig-zag line with nonmetals on the right and metals on the left.The alkali metals are listed under group 1The alkaline earth metals are listed under group 2The noble gases are listed under group 18The transition metals are listed from group 3 to group 12.The halogens are listed under group 17The inner transition elements (f-block) are listed at the bottom separately.So, from this, we can match the given elements as:
Titanium -metal
gold - metal,
Argon - noble gas
Thallium -metal. transition metal
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How many grams of solid sodium cyanide should be added to 1.00 L of a 0.119 M hydrocyanic acid solution to prepare a buffer with a pH of 8.809
Answer:
1.62 g
Explanation:
Given that:
Concentration of HCN = 0.119 M
Assuming the ka 4.00 × 10⁻¹⁰
The pKa of HCN (hydrocyanic acid) = -log (Ka)
= - log ( 4.00 × 10⁻¹⁰)
= 9.398
pH of buffer = 8.809
Using Henderson Hasselbach equation:
[tex]pH = pKa + log \dfrac{[conjugate\ base ]}{acid}[/tex]
[tex]pH = pKa + log \dfrac{[CN^-]}{[HCN]}[/tex]
[tex]8.809 = 9.398 +log \dfrac{[CN^-]}{[HCN]}[/tex]
[tex]log \dfrac{[CN^-]}{[HCN]}= 8.809 - 9.398[/tex]
[tex]log \dfrac{[CN^-]}{[HCN]}= -0.589[/tex]
[tex]\dfrac{[CN^-]}{[HCN]}= 0.2576[/tex]
[CN^-] = 0.2576[HCN]
[CN^-] = 0.2756 (0.119) L
[CN^-] = 0.033 M
∴
The amount of NaCN (sodium cyanide) is calculated as follows:
[tex]= 1.00 L \times \dfrac{0.033 \ mol \ NacN }{1 \ L } \times \dfrac{49.01 \ g}{1 \ mol \ of \ NacN}[/tex]
= 1.62 g
After mixing the solutions in a separatory funnel, the stopper should be ______ and the liquid should be _______ and the layers allowed to separate. When you get close to the interface between the layers, ______ the funnel and turn over _______ heat up until the first layer is collected get eye level with to collect the second layer. _______
Answer:
Hence,
1) removed
2) drained through the stopcock
3) get eye level with
4) slow the draining
5) switch to a new flask
Explanation:
After mixing the solutions in a separatory funnel, the stopper should be removed and the liquid should be drained through the stopcock, and the layers allowed to separate. When you get close to the interface between the layers, get eye level with the funnel and turn over to slow the draining heat up until the first layer is collected. Switch to a new flask get eye level with it to collect the second layer.
The half life for the radioactive decay of potassium-40 to argon-40 is 1.26×109 years. Suppose nuclear chemical analysis shows that there is 0.359 mmol of argon-40 for every 1.000mmol of potassium-40 in a sample of rock. Calculate the age of the rock.
Answer:
2.42x10⁹ years is the age of the rock
Explanation:
The decay of an isotope follows the equation:
Ln[A] = -kt + Ln[A]₀
Where [A] is amount of isotope after time t, k is decay constant and [A]₀ is the initial amount of the isotope
To find decay constant from half-life:
k = ln2 / half-life
k = ln2 / 1.26x10⁹years
k = 5.501x10⁻¹⁰ years⁻¹
As in the reaction, K-40 produce Ar-40:
[A] = 0.359mmol
[A]₀ = 0.359mmol + 1.000mmol = 1.359mmol
Replacing:
Ln[0.359mmol] = -5.501x10⁻¹⁰ years⁻¹t + Ln[1.359mmol]
-1.3312 = -5.501x10⁻¹⁰ years⁻¹t
t = 2.42x10⁹ years is the age of the rock
Atoms of element X have 12 times the mass of atoms of oxygen, and atoms of oxygen have 16 times the mass of atoms of hydrogen. What is the mass of atoms of element X on a scale on which atoms of hydrogen have a mass of 1?
A. 16/12
B. 12/16
С. 12 x 16
D. 16-12
E. 1216
Answer:
C. 12 × 16
Explanation:
Let mH be the mass of atoms of hydrogen and mO be the mass of atoms of oxygen. The atoms of oxygen have 16 times the mass of atoms of hydrogen. That is,
mO = 16 mH [1]
Let mX be the mass of the atoms of X. Atoms of element X have 12 times the mass of atoms of oxygen. That is,
mX = 12 mO [2]
If we substitute [1] in [2], we get
mX = 12 × 16 mH
If mH is 1, we get,
mX = 12 × 16 × 1
mX = 12 × 16
Which of the following is not generally a characteristic of metal?
Ductility
O
Malleability
High melting point
Low boiling point
Anew fictitious element was discovered. It is a metal named jolmium, J,and it has three valence electrons. If it combineswith iodine it forms jolmium iodide. Answer the following questions.a.Is this compound ionic or covalent
a. Is this compound ionic or covalent?
b. What is the formula of Jolmium iodide?
c. What is the charge on the metal J in this compound?
d. Explain how you know that is the charge?
Answer:
A new fictitious element was discovered.
It is a metal named jolmium, J, and it has three valence electrons.
If it combines with iodine it forms jolmium iodide. Answer the following questions.
a.Is this compound ionic or covalent
b. What is the formula of Jolmium iodide?
c. What is the charge on the metal J in this compound?
d. Explain how you know that is the charge?
Explanation:
It is given the element jolmium J is a metal with three valence electrons.
Since metals are highly electropositive, they lose electrons easily and form cations (Ions with a positive charge).
[tex]J^{3+}[/tex] ion will be formed.
b) The formula of jolmium iodide is shown below:
[tex]J^{+3} I^{-1}\\The formula becomes:\\JI_{3}[/tex]
a) The compound is ionic in nature.
Since the compound formed between a metal atom and a nonmetal atom will take place by transfer of electrons.
Hence, it is ionic in nature.
c) The charge on the metal J in this compound is +3.
d) Given J has three valence electrons.
That means it can lose three electrons to form a bond.
So, its valency is three.
A chemistry student needs 15.0 g of methanol for an experiment. She has available 320. g of 44.4% w/w solution of methanol in water. Calculate the mass of solution the student should use. If there's not enough solution, press the "No solution" button. Round your answer to 3 significant digits.
Answer:
33.8 g Solution
Explanation:
A chemistry student needs 15.0 g of methanol for an experiment. The concentration of ethanol in the solution is 44.4% w/w, that is, there are 44.4 g of methanol every 100 g of solution. The mass of solution that would contain 15.0 g of methanol is:
15.0 g Methanol × 100 g Solution/44.4 g Methanol = 33.8 g Solution
Since 33.8 g are required and 320. g are available, there is enough solution for the requirements.
Convert 400.0 ng/dL to cg/L
Answer:
.04 cg/L
Explanation:
Desclony When Fe(NO3)2 dissolves in water, what particles are present in the solution?
Answer:
hjfhgjgjgjghgjgjhgjhhjh
Sodium azide, NaN3, the explosive compound found in automobile air bags, decomposes according to the following equation: 2NaN3(s)right arrow 2Na(s) + 3N2(g)
What mass of NaN3 is required to provide the nitrogen needed to inflate an 80.0-L bag to a pressure of 1.3 atm at 27 degree C? What is the density of the gas under these conditions?
Answer:
1.9 × 10² g NaN₃
1.5 g/L
Explanation:
Step 1: Write the balanced decomposition equation
2 NaN₃(s) ⇒ 2 Na(s) + 3 N₂(g)
Step 2: Calculate the moles of N₂ formed
N₂ occupies a 80.0 L bag at 1.3 atm and 27 °C (300 K). We will calculate the moles of N₂ using the ideal gas equation.
P × V = n × R × T
n = P × V / R × T
n = 1.3 atm × 80.0 L / (0.0821 atm.L/mol.K) × 300 K = 4.2 mol
We can also calculate the mass of nitrogen using the molar mass (M) 28.01 g/mol.
4.2 mol × 28.01 g/mol = 1.2 × 10² g
Step 3: Calculate the mass of NaN₃ needed to form 1.2 × 10² g of N₂
The mass ratio of NaN₃ to N₂ is 130.02:84.03.
1.2 × 10² g N₂ × 130.02 g NaN₃/84.03 g N₂ = 1.9 × 10² g NaN₃
Step 4: Calculate the density of N₂
We will use the following expression.
ρ = P × M / R × T
ρ = 1.3 atm × 28.01 g/mol / (0.0821 atm.L/mol.K) × 300 K = 1.5 g/L
Which is the balanced version of the half-reaction below?
H2S → S+H+
Answer:
C. [tex]H_2S\rightarrow S+2H^++2e^-[/tex]
Explanation:
Hello there!
In this case, according to the given chemical reaction, it turns out possible to realize there is one sulfur atom on each side of the chemical equation but two hydrogen atoms on the left and one on the right, which means the latter must be balanced in agreement to the law of conservation of mass.
In such a way, by setting a 2 on H⁺, the reaction will be balanced:
[tex]H_2S\rightarrow S+2H^+[/tex]
Now, we count the transfer electrons for sulfur from -2 to 0 as 2e⁻ on the right, which will match with the option C.
[tex]H_2S\rightarrow S+2H^++2e^-[/tex]
Regards!
The oxidation number of nitrogen in NO2 is:
a. 1.
b. 2.
c. 3.
d. 4.
e. 5.
f. None of the above.
Answer:
Option D. 4
Explanation:
The oxidation number of nitrogen (N) in NO₂ can be obtained as follow:
Oxidation number of O = –2
Oxidation number of N =?
N + 2O = 0
N + 2(–2) = 0
N – 4 = 0
Collect like terms
N = 0 + 4
N = +4
Thus, the oxidation number of nitrogen (N) in NO₂ is +4
Which of the following expressions is the correct equilibrium constant expression for the equilibrium between dinitrogen tetroxide and nitrogen dioxide? N subscript 2 O subscript 4 space left parenthesis g right parenthesis space rightwards arrow over leftwards arrow 2 space NO subscript 2 space left parenthesis straight g right parenthesis
Answer:
Correct answer:
The equilibrium expression is defined as the ratio of the concentration of products divided by the concentration of the reactants. Each reactant or product is raised to the power corresponding to its coefficient in the balanced chemical equation.
Explanation:
55:28
An object is moving across a surface, but it does not gain or lose speed. Which best describes the object's force?
The net force is positive.
The net force is zero.
The positive force is greater than the negative force.
The negative force is greater than the positive force.
ke this and totum
Save and Exit
Next
S
Answer:
The correct answer is - The net force is zero.
Explanation:
When an object moves on the surface with the same or constant acceleration which means there is no gain or loss of the speed it shows that all the forces of the object are at a point of zero.
If there would be any force applied on the object there must be some change in the velocity or acceleration but in this case there is no loss or gain of speed which means there is the object's net force is zero.
Therefore, option B is correct.
Some chemical bonds are considered molecules while others are considered compounds.
Explain what the difference is and provide one example for each.
Molecule is the general term used to describe any atoms that are connected by chemical bonds. Every combination of atoms is a molecule. A compound is a molecule made of atoms from different elements. All compounds are molecules, but not all molecules are compounds.
One example of a molecule is [tex]Cl_2[/tex] (chlorine).
Examples of a compound is NaCl (sodium chloride) or [tex]H_2O\\[/tex] (water)
Water is considered to be a diatomic molecule because it composed of two different atoms. True or false?
Answer:
false
Explanation:
False, water is a polyatomic molecule made up of two atoms of oxygen and 1 atom of hydrogen.
Explanation:
The monoatomic molecule is composed of a single atom of an element.For example: Helium(He) , argon(Ar) etc.The diatomic molecule is composed of two atoms of the same or different elements.For example: hydrochloric acid (HCl), sodium chloride (NaCl) etc.The polyatomic molecule is composed of three or more than three atoms of the same or different elements.For example: water ([tex]H_2O[/tex]), sodium hydroxide(NaOH) etc.So, from this, we can conclude that water is a polyatomic molecule made up of two atoms of oxygen and 1 atom of hydrogen.
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What is represented by the chemical formula
PbCl2(s)?
A) a substance
B) a solution
C) a homogeneous mixture
D) a heterogeneous mixture
A hemil reation
Answer:
d
Explanation:
cuaase that it sirhal
The chemical formula PbCl₂(s) represented by:
A) a substance
The chemical formula PbCl₂(s) represents a substance. A substance is a single, pure chemical entity with a definite composition. It can be an element, a compound, or an alloy.
A solution is a homogeneous mixture of two or more substances. A homogeneous mixture is a mixture in which the components are evenly distributed throughout the mixture.
A heterogeneous mixture is a mixture in which the components are not evenly distributed throughout the mixture.
A reaction is a process in which one or more substances are transformed into one or more new substances.
Therefore, the chemical formula PbCl₂(s) represents a substance, and the answer is (A).
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2. On the periodic table, what is the difference between a group (or family) and a period?
Answer:
On the periodic table,periods are horizontal rows (across) the periodic table while groups are vertical columns (down) the table.We have groups in the periodic table like transition metals,rare earth,alkali metals ,alkaline earth metals halogens and noble gases
Answer:
Horizontal row call period and vertical column called group!
Physical,chemical, reaction procedure, shape,size, enthalpy of dissociation, bonding,non bonding, various things that segregated group and period....
Helppp!
Is astatine (At), atomic number 85, a metal or nonmetal? Why?
Answer:
At is a metalloid
Explanation: Meaning that it displays some of the characteristics of a metal but can also display characteristics of nonmetals. Silicon is one such element. Elemental Silicon has a dark lustrous metallic appearance but it is quite brittle. Some authorities include Astatine as a halogen as it has seven electrons in its valence shell placing it just below iodine in period 17 VIIA. Additionally, because Astatine is only ever found naturally as the result of radioactive decay from more dense elements it is the rarest naturally occurring element in Earth's crust.
I hope this helps at least a little.
Regards,
JR Holt
Chemist retired
carbon dioxide gas evolve during the fermentation of sugar which was collected at 22.5°C and 0.945 ATM after perfect strangers in the volume was found to be 25.0 ML how many grams of carbon dioxide were collected
Answer:
0.043 grams
Explanation:
We can find the mass of carbon dioxide as follows:
[tex] m = n*M [/tex]
Where:
n: is the number of moles
M: is the molar mass = 44.01 g/mol
First, we need to calculate the number of moles. We can use the Ideal gas equation:
[tex] PV = nRT [/tex]
Where:
P: is the pressure = 0.945 atm
V: is the volume = 25.0 mL
R: is the gas constant = 0.082 L*atm/(K*mol)
T: is the tempearture = 22.5 °C
[tex]n = \frac{PV}{RT} = \frac{0.945 atm*25 mL*\frac{1 L}{1000 mL}}{0.082 L*atm/K*mol*(22.5 + 273) K} = 9.75 \cdot 10^{-4} moles[/tex]
Hence, the mass is:
[tex]m = 9.75 \cdot 10^{-4} moles*44.01 g/mol = 0.043 g[/tex]
Therefore, 0.043 grams were collected.
I hope it helps you!
Consider the following events that take place when rip currents occur.
A. Waves travel to the beach.
B. Waves are trapped by the sandbars.
C. Waves reach the shore and go back to the ocean.
D. Waves speed up and flow between the sandbars.
E. Waves are broken by the sandbars.
Which list shows the order of events in the production of rip currents?
A weather balloon containing helium with a volume of 410.0 L rises in the atmosphere and is cooled from 17∘
∘
C to -27∘
∘
C. The pressure on the gas is reduced from 110.0 kPa to 25.0 kPa. What is the volume of the gas at the lower temperature and pressure? What law did you use to solve?
Answer:
V₂ = 1500 Liters ( 2 sig. figs.)
Explanation:
Given the following gas law variables:
P₁ = 110.0KPa P₂ = 25KPa
V₁ = 410 Liters V₂ = ?
T₁ = 17°C ( = 290K) T₂ = -27°C ( = 248K)
P₁V₁/₁T₁ = P₂V₂/T₂ => V₂ = V₁(P₁/P₂)(T₂/T₂)
V₂ = 410L(110.0KPa/25KPa)(248k/290K) = 1542 L (calc. ans.)
V₂ = 1500 Liters ( 2 sig. figs.)
An ideal gas is made up of gas particles that...
(A) ...have volume.
(B) ... attract each other.
(C)...can be liquified.
(D) ... are in random motion.
Answer:
Its D Are in random motion
i hope it will help you if not soo sorry :)
Based on your knowledge of factors affecting the rate of reaction, why is there a danger of explosions in places such as flour mills and coal mines where there are large quantities of powdered, combustible materials?
Answer:
See Explanation
Explanation:
Rate of reaction refers to how quickly or slowly a reaction proceeds. The rate of reaction depends on certain factors.
Two among the factors that affect the rate of reaction are the concentration of reactants and the surface area of reactants.
The more the concentration of reactants, the faster the rate of reactants because there is a high possibility of collision between reactants. Also, the higher the surface area of reactants, the greater the rate of reaction.
In flour mills and coal mines where there is a large amount (concentration) of combustible materials and the particles are powdered (high surface area), there is a greater risk of explosion due to a high rate of reaction owing to a combination of the two factors discussed above.
Compare the solubility of calcium sulfite in each of the following aqueous solutions:
a. 0.10 M Ca(CH3COO)2
b. 0.10 M K2SO3
c. 0.10 M NaNO3
d. 0.10 M KCH3COO
1. More soluble than in pure water.
2. Similar solubility as in pure water.
3. Less soluble than in pure water.
Answer:
0.10 M Ca(CH3COO)2- Less soluble than in pure water.
0.10 M K2SO3- Less soluble than in pure water.
0.10 M NaNO3 - More soluble than in pure water.
0.10 M KCH3COO- Similar solubility as in pure water.
Explanation:
We have to cast our minds back to the idea of common ions effect. If any ion is already present in solution, the presence of that ion in solution prevents any solute containing a common ion with the solution from dissolving in that solution. In order words, the presence of a common ion makes a solute less soluble in a solvent than it is in pure water.
For instance, 0.10 M Ca(CH3COO)2 and K2SO3 both contain Ca^2+ and SO3^2- ions respectively which are also contained in the solute calcium sulfite.
The presence of these common ions in solution makes calcium sulfite less soluble in these solutions than it is in pure water because the equilibrium position for the dissolution of the solute lies towards the left hand side.
However, calcium sulfite is more soluble in 0.10 M NaNO3 than in pure water due to displacement reaction between the ions in solution.
The solubility of calcium sulfite and 0.10 M KCH3COO in pure water is quite comparable.