Explanation:
SOLID
Sodium hydroxide exists in the solid phase at room temperature. You would find it in the lab as hemispherical white solid pellets. The phase of a substance depends on temperature and pressure. As you heat a solid, it will melt and change to the liquid phase.
What is indicated by 'A' in the figure below? A. -VE B. +Ea C. -Ea D. +VE
Answer:
+VE
Explanation:
If we look at the reaction profile pictured in the question, we can easily identify A as the enthalpy of the reaction. The enthalpy of reaction (ΔHrxn) is usually defined as the difference between the total enthalpy (heat content) of the products of a reaction and the total enthalpy (heat content) of the reactants in that reaction.
Looking at the figure, we can see that the enthalpy of products is greater than the enthalpy of reactants, hence ∆Hrxn is positive as stated in the answer above.
If a chemist wants to make one liter of a 1.5 M solution of NaOH from a stock solution of 2.5 M NaOH, how many milliliters of the stock solution would the chemist need to use?
A.6.0 x 102 mL
B. 0.60 mL
C. 1.7 x 103 mL
Answer:
0.60 mL
Explanation:
1. Set up the equation using Vi = MfVf / Mi
Vi = (1.5M · 1L) / 2.5M
2. Solve
1.5 / 2.5 = 0.6
Complete this sentence. If mass remains the same while the volume of a substance ________, the density of the substance will_______________.
Answer:
If mass remains the same while the volume of a substance changes, the density of the substance will also change.
Answer:
BELOW
Explanation:
If mass remains the same while the volume of a substance decreases the density of the substance will increase.
How does antifreeze rely on colligative properties to work?
A. It causes the vapor pressure to increase and the increased outward pressure of the gasoline vapors prevents it from solidifying into ice.
B. It causes freezing point elevation which raises the temperature of the gasoline without letting it freeze.
C. It causes freezing point depression which requires the gasoline to reach a much lower temperature before freezing.
D. It causing boiling point elevation, which raises the temperature of the gasoline without letting it boil so that it can resist the cold.
WILL GIVE BRAINLIEST FOR CORRECT!!!
It causes freezing point depression which requires the gasoline to reach a much lower temperature before freezing. Hence, option C is correct.
What is the freezing point?Whenever a solute is added to a solution/solvent, it leads to depression in the freezing point of that solution/solvent. Depression in the freezing point of a solution on the addition of a solute is a colligative property.
A colligative property is a physical property which depends upon the number of solutes added not on the nature of solutes which means it does not matter whether we are adding 1000 particles of sugar or salt in water, the depression in the freezing point will occur by the same °C. Also, the more a solute is added the more will be the depression at the freezing point.
The formula for depression at the freezing point is mentioned as under:
Δ T = K x m
where Δ T = freezing point depression;
K = cryoscopic constant;
m = molality of the solution.
For example, The freezing point of water is 0 °C but as soon as we add a 92 gm solute like NaCl (common salt) in 1000 gm of water, its freezing point will be lower to −3.72 °C.
Hence, option C is correct.
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calculate the pH of 500cm3 of 0.2mol/dm3 Ca(OH2), assume complete ionisation
Answer:
The pH of 500 cm³, 0.2 mol/dm³, Ca(OH₂) is ≈ 13.6
Explanation:
The given parameters are;
Concentration of the calcium hydroxide, Ca(OH₂) = 0.2 mol/dm³
Volume of the calcium hydroxide, Ca(OH₂) = 500 cm³
Given that the calcium hydroxide, Ca(OH₂), undergoes complete ionization in water, complete dissociation, we have;
Ca(OH₂) ⇄ Ca²⁺ + 2 OH⁻
Therefore, we have;
2 moles of [OH⁻] for each mole of Ca(OH₂) which gives the concentration of [OH⁻] as
[OH⁻] = 2 × 0.2 ≈ 0.4 mol/dm³
The pH is given by the formula
pH = 14 + ㏒₁₀ [OH⁻]
pH = 14 + ㏒₁₀ (0.4) = 14 - 0.3979 = 13.6021 ≈ 13.6
The pH of the 500 cm³ 0.2 mol/dm³ Ca(OH₂) ≈ 13.6.
explain why ply(ethene) can become a pollutant?
Answer:
ipotseeeeeeeeeeeeeeee
Why are ionic crystals soluble in water?
A. The covalent bonds in the ionic crystal can easily reshape to bond with the water molecules, allowing it to dissolve.
B. The water slides the layers of the ionic crystal lattice so that positive charges line up with positive charges. They repel
each other and break the crystal apart.
C. Partial charges in water molecules attract the charges in the atoms of the ionic crystal, pulling the atoms off the crystal.
D. They are not. The positive and negative charges in the ionic lattice are stronger than the partial charges in the water.
Answer:
C. Partial charges in water molecules attract the charges in the atoms of the ionic crystal, pulling the atoms off the crystal.
Explanation:
Water consists of partial positive and hydrogen ions and partial negative oxygen ions. The ionic crystals also dissociate into ions when in water.These partial charges and ability of ionic compounds to dissociate in water are the main reason why ionic crystals dissolve in water.
The partial charges in the water molecules form a strong attraction towards the charges in the atoms of ionic crystals. This then pulls the atoms from the crystals and ends up in the dissolution of the ionic crystals.
using methyl ,phenolphthalein and litmus name an acid
Answer:
These are two types of indicators which show a solution is either an acid a natural or an alkali solution
Explanation:
Hope this helps :)
In the image above the ruler is measuring in centimeters. The blue cylinder falls somewhere between 2.7cm and 2.8cm according to the ruler. Since we can estimate the last digit I would say that the length of the cylinder is 2.76cm. Since I am estimating any number 2.72cm or 2.78cm could also be correct.
Why would 2.755 not be a correct measurement according to estimating the last digit?
Answer:
The accuracy of the measuring ruler is given as tenth of a centimetre and given that the image above the ruler is measuring in between a tenth of a centimetre, it is therefore measuring at a higher accuracy than the ruler
The least count of the vernier scale = (Main scale's smallest reading)/(Number of vernier scale divisions)
Where;
Main scale's smallest reading = 0.1 cm
Number of vernier scale divisions = 10
We have;
The least count of the vernier scale =0.1/10 = 0.01
The image above the ruler, (the vernier scale measurement) should therefore measure at hundredth of a centimetre and the value of the measurement given to two places of decimal, 2.XX, as such 2.755 which is of a level of accuracy of a thousandth for the vernier scale would not be correct.
Explanation:
Di- Ethyl zinc is a chemical used in the library to protect books from worms, its composition is 53% Zinc, 38.9% Carbon, and 8.1% Hydrogen (At mass of Zn=65.4, C=12, H=1). Find the empirical formula of a compound
Answer:
ZnC4H10
Explanation:
The empirical formula of a compound refers to the formula that gives the simplest whole number ratio of each atoms of the elements in the compound.
The empirical formula is calculated thus:
The given percentages in the question represent the mass in grams of each element in the compound.
Zinc= 53%, C= 38.9%, H= 8.1% which represents 53g, 38.9g and 8.1g of each element respectively.
Molar Mass of Zn= 65.4 g/mol
Molar Mass of C= 12 g/mol
Molar Mass of H= 1 g/mol
Step 1: Divide the mass of each element by the molar mass given to convert to moles:
Zn= 53/65.4 = 0.81moles
C= 38.9/12 = 3.24moles
H= 8.1/1 = 8.1moles
Step 2: Divide each mole value by the smallest number of moles calculated, which is 0.81moles:
Zn= 0.81/0.81 = 1
C= 3.24/0.81 = 4
H= 8.1/0.81= 10
This is the mole ratio represented in the subscript of each element in the empirical formula:
That is, Zn (1) C (4) H (10)
Empirical formula= ZnC4H10
3.87 moles of iron bromide yielded10.4 moles of sodium bromide
Answer: 89.57 %
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If a gas displays a solubility of 0.00290M at a partial pressure of 125 kPa, what is the proportionality constant for this gas in this solvent and at this temperature?
Answer:
The proportionality constant ( Henry’s constant) = 2.32 * 10^-5 M/kPa
Explanation:
Here in this question, we are concerned with calculating the proportionality constant for this gas.
Mathematically, we can get this from Henry law
From Henry law;
Concentration = Henry constant * partial pressure
Thus Henry constant = concentration/partial pressure
Henry constant = 0.00290 M/125 kPa = 2.32 * 10^-5 M/kPa
Which substance has the highest melting point? Select one: a. sugar b. Oxygen c. Diamond
Answer:
Diamonds
Explanation:
The melting point of sugar is 186C
The melting point of oxygen is -218C
The melting point of diamonds are 4078C
Therefore diamonds have the highest melting point.
You can also think of their structures, as diamonds have a covalent network structure, meaning they are really strong and have a high melting point
Oxygen has a covalent molecular structure
Sugar has a much weaker covalent network structure
Air is an example of a mixture because the elements and compounds that make up air retain their individual properties. T or F
Answer:
True
Explanation:
This is true because no chemical bonding or change was involved only mechanical mixing.
The density of a 39 gram object with a volume of 5 cm is
Answer:
[tex]\huge\boxed{\sf D = 7.8 \ g/cm^3}[/tex]
Explanation:
Density = Mass / Volume
Where Mass = 39 g and Volume = 5 cm³
So,
[tex]\sf Density = \frac{39}{5} \\Density = 7.8 g/cm^3[/tex]
A baseball has a mass of 135 grams and a softball has a mass of 270 grams. In which of the following situations would they have the same momentum? The baseball and softball are thrown at the same speed in the same direction.
Answer:
The baseball is thrown twice as fast as the softball in the same direction.
Explanation:
The identity of an element is determined by
A. the number of neutrons
B. the weight of the nucleus
C. the number of protons
D. the number of electrons
The answer is Number of Protons !
Answer: D. the number of protons
Explanation: The number of protons shows you what the Atomic number of an element is on the Periodic table of elements.
The identity of an element is primarily determined by the number of protons it possesses. The Option C.
What determines the identity of an element?Each element on the periodic table has a unique number of protons in its nucleus which is referred to as its atomic number. This fundamental property of an element distinguishes it from other elements and determines its place on the periodic table.
While number of neutrons and electrons can vary within an element, it is the number of protons that defines its identity. Thus, the correct answer is C: the number of protons.
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percentage of carbon in urea
The percentage of carbon in urea is [CO(NH 2) 2] is 20%
please someone explain this I dont get it at all. how do we know that the 4th electron came from 2p because it's at 4th ionisation? why is it talking about 3s?? how do overall know that aluminium is in group 3 from the table??? thanks
Is wax a good conductor of electricity?
what is mean by stakeholder
Answer:
a stakeholder is a party that has an interest in a company and can either effect or be affected by the business. the primary stakeholder in a typical corporation are its investors , employees, customers and supplies.BRAINLIEST!!! ❣
How do scientists use ice to study ancient climates?
A. through glacial deposits and ice cores
B. through glacial deposits and ice ages
C. through ice cores and pollen grains
D. through pollen grains and ice ages
Which greenhouse gas is produced by commercial refrigeration and air conditioning systems?
A. carbon dioxide
B. fluorinated gas
C. nitrous oxide
D. methane
Explanation:
the first question's answer is a
the second question's answer is c
Please help me... how do I draw this...
Draw diagrams to show the bonding in each of the following compounds:
a) calcium fluoride (CaF2)
Answer:
Hope it helps!!!
............
In the Lewis structure, the Ca atom donates its two valence electrons to two F atoms.
The bonding in calcium fluoride (CaF₂) involves the transfer of electrons from calcium (Ca) to fluorine (F), resulting in the formation of ionic bonds.
Each F atom gains one electron to achieve a stable electron configuration of eight electrons in its outermost energy level. The electrostatic attraction between the positively charged Ca ion (Ca²⁺) and the negatively charged F ions (F⁻) holds the compound together.
It's important to note that the diagram represents a simplified 2-dimensional representation of the compound's structure. In reality, the compound adopts a three-dimensional crystal lattice structure, with each Ca ion surrounded by eight F ions and each F ion surrounded by four Ca ions.
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Why is graphite slippery when pressed? Select one: a. covalent bonds break b. hexagonal layers slide c. molecules of graphite slide
Answer:
hexagonal layers slide
Explanation:
The layers in graphite can slide over each other because the forces between them are weak. The delocalised electrons are free to move through the structure, so graphite can conduct electricity.This makes graphite slippery, so it is useful as a lubricant .
i think it's right
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Which of the following statements about a chemical reaction is false? Group of answer choices The phases in a chemical reaction tell us the state of the reactants and the products. An individual coefficient, with no reactant or product, in a balanced equation is meaningless. The subscripts in a balanced equation tell us the number of atoms in a molecule.
Answer:
Option B
Explanation:
Let us go through each of the options individually.
option A.
he phases in a chemical reaction tell us the state of the reactants and the products.
This is true because phases representations such as s, l , g and q tells us the state of the reactants if they are in the solid or liquid or gaseous or aqueous state of matter respectively. So this is not our answer.
option B
An individual coefficient, with no reactant or product, in a balanced equation is meaningless.
This option is correct, because in every reaction, there must be the reactant and product present.
option C
The subscripts in a balanced equation tell us the number of atoms in a molecule.
This is correct. Consider the equation below;
2H₂ + O₂ --> 2H₂O
In the reactant phase, the subscripts tells us that we have just two atoms of oxygen present.
Which of the following is an example of a consumer? Tree Sun Rabbit Mushroom
Answer:
rabbit
Explanation:
Answer:
rabbit
Explanation:
the rabbit is the consumer because the sun "produces" the tree and mushroom, the rabbit comes along and eats the mushroom which was produced by the sun.
What does the VSEPR theory describe
Answer:
The shape of a molecule based on the number of electron pairs on the valence shell of its central atom
Explanation:
The improvement of the Sidgwick-Powell theory came to be known as the Valence Shell Electron Pair Repulsion theory (VSEPR). This theory approaches the determination of molecular shape from the perspective of the number of electron pairs on the valence shell of the central atom in the molecule.
Electron pairs on the valence shells of atoms leads to repulsion. Repulsion between two lone pairs is greater than repulsion between a lone pair and a bond pair which is also greater than repulsion between two bond pairs.
Lone pairs cause more repulsion, hence they distort molecules from the ideal shape predicted based on their electron domain geometry.
what is the question tag for Lynne speaks french and German
Answer:here is it...
Explanation:
The question tag for the statement "Lynne speaks French and German" would be "doesn't she?"
The question tag is a short question added to the end of a statement to turn it into a question and seek confirmation or agreement. It is usually formed by using an auxiliary verb opposite in polarity to the main verb in the statement.
In the given statement, "Lynne speaks French and German," the main verb is "speaks." Since the main verb is in the affirmative form, the question tag should use the negative form.
Therefore, we use the auxiliary verb "doesn't" (the negative form of "does") and add the pronoun "she" to match the subject of the statement.
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Calculate the number of molecules present in 2.50 mol H2S?
A. 1.51 x 10^24 molecules
B. 2.50 x 10^23 molecules
C. 1.5 x 10^23 molecules
One mole of H₂S gas contains 6.022 × 10²³ H₂S molecules. Hence, 2.50 mol of H₂S contains 1.50 × 10²⁴ molecules. Thus, option A is correct.
What is Avogadro number?Any substance containing 6.022 × 10²³ number of atoms is called one mole of that substance. This number is called Avogadro number. Thus, one mole every elements contains Avogadro number of atoms.
Similarly a compound is made of molecules. One mole of a compound contains 6.022 × 10²³ number of molecules. The mass of a compound with Avogadro number of molecules is called its molar mass.
As any other compound, one mole of H₂S contains 6.022 × 10²³ molecules. Therefore, the number of molecules in 2.50 moles of H₂S is :
2.50 moles × 6.022 × 10²³ molecules/mol = 1.50 × 10²⁴molecules
Hence, the number of molecules present in 2.50 moles of H₂S is 1.50 × 10²⁴.
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A sample of kerosene has a mass of 36.4g. It’s volume is 45.6mL. What is the density of kerosene?
Answer:
Density = 0.8 g/cm³Explanation:
The density of an object can be found using the formula
[tex]Density(\rho) = \frac{mass}{volume} [/tex]From the question
mass of kerosene = 36.4 g
volume of kerosene = 45.6 mL
To find the density substitute the values into the above formula and solve
We have
[tex]Density = \frac{36.4}{45.6} [/tex]= 0.7982
We have the final answer as
Density = 0.8 g/cm³Hope this helps you
