Please help me...
Atoms of elements X, Y and Z have 16, 17 and 19 electrons, respectively. Atoms of argon have 18 electrons.
a Determine the formulae of the compounds formed by the combination of the atoms of the elements:
(i) X and Z
(ii) Y and Z
(iii) X with itself.
b In each of the cases shown in
A (i)–(iii) above, name the type of chemical bond formed.
c Give two properties you would expect to be shown by the compounds formed in an (ii) and an (iii).
Answer:
a 1) XZ2
2) YZ
3) X2
b 1) Ionic bond
2) Ionic bond
3) covalent bond
c) ionic compounds has high melting and boiling point
ionic compounds can conduct electicity in aqueous form
covalent compounds have electrons shared between the atoms
covalent compounds have lower melting point compared to ionic compound
Answer:
(i) XZ = Potassium Sulfide [K2SO4]
(ii) YZ = Potassium Chloride [KCI]
(iii) X = Sulfur [S]
b) (i) Ionic Bond. (ii) Ionic Bond. (iii) Covalent Bond.
c) (i) Ionic compounds have high melting and boiling points.
(ii) Ionic compounds can conduct electricity in a molten state or a solution as they have ions that can move and carry charge.
(iii) Covalent compounds have low melting and boiling points.
(iv) Covalent compounds can not conduct electricity as all electrons are involved in bonding so there are no free electrons or ions to carry the charge.
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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
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
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.
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
explain why ply(ethene) can become a pollutant?
Answer:
ipotseeeeeeeeeeeeeeee
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
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
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.
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.
Perform the forlowing
mathematical operation, and
report the answer to the correct
number of significant figures.
4568/13 = [?]
Answer:
[tex]\large \boxed{350}[/tex]
Explanation:
In multiplication and division problems, the answer can have no more significant figures than the number with the fewest significant figures.
My calculator gives the result:
[tex]\dfrac{4568}{13} = 351.3846154[/tex]
4658 has four significant figures.
13 has two significant figures.
You must round to two significant figures.
That is, you drop all the digits to the right of the 5 — the red line in Fig. 1 below. You are rounding to the nearest ten.
To round a number to the nearest ten, you look at the number in the ones place (1). See Fig. 2.
If the number to be dropped — the digit in the ones place — is less than 5, you drop the digit in the ones place (Fig. 3). It becomes a zero.
The number in the tens place is a trailing zero. It is not significant.
[tex]\text{The quotient of $\dfrac{4658}{13}$ is $\large \boxed{\mathbf{350}}$}[/tex]
What is the colour formed when N2O is bubbled into a solution of acidified FeSO4
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:
calculate the amount in moles of a gas which occupies 250cm3 at s.t.p
Answer: 0.01 moles (I am guessing)
Explanation:
Firstly, cm3 and ml are equal to one another, therefore 250cm3 can also be written as 250 ml. I Googled and found that ideally, one mole of gas will occupy a volume of 22.4 L (22,400 ml) at s.t.p. 250 ml out of 22,400 ml is 0.01 rounded, therefore I assume that is the answer. About 0.01 mole occupies 250 cm3 at s.t.p.
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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
percentage of carbon in urea
The percentage of carbon in urea is [CO(NH 2) 2] is 20%
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.
Read more about element identity
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How would a decrease in volume affect the following reaction? N2 (g) + O2 (g) Two arrows stacked on top of each other. The top arrow points to the right. The bottom arrow points to the left. 2NO(g) (1 point) The equilibrium would shift to the right. The equilibrium would shift to the left. There would be no change to equilibrium. The affect on equilibrium cannot be determined.
Answer:
Explanation:
N₂(g) + O₂(g) ⇄ 2NO( g )
We shall apply Le Chatelier's principle to see the effect of decrease in volume or increase in concentration on the effect of state of equilibrium in the reaction given .
In this reaction 1 volume of nitrogen gas reacts with 1 volume of oxygen to give 2 volume of NO gas . In total there is no change in volume due to reaction . So when we change the volume , the concentration of reactant and product will affect the rate of forward and reverse reaction . Overall there will be no change in the state of equilibrium . The equilibrium will neither shift to the right nor will shift to the left.
It will remain unchanged .
Which of the following processes is exothermic? Group of answer choices Allowing meat to thaw after taking it out of the freezer Popsicle melting on a warm summer day Boiling water in a beaker to convert it to steam Rolling a ball up a hill Reacting hydrogen and oxygen gases to make water
Answer:
Reacting hydrogen and oxygen gases to make water
Explanation:
Exothermic means that energy is released into the environment, so let's go through the process of elimination.
Allowing meat to thaw after taking it out of the freezer - NO it is endothermic, and takes energy/heat from the environment to thaw.
Popsicle melting on a warm summer day - NO also endothermic, the opposite of exothermic.
Boiling water in a beaker to convert it to steam - NO because we need to add heat, so it doesn't release any energy.
Rolling a ball up a hill - NO, for a ball to roll up a hill, it needs energy from something else, so it's not exothermic.
Reacting hydrogen and oxygen gases to make water - YES this reaction makes new bonds, which releases energy, so this is exothermic.
Among the following choices reacting hydrogen and oxygen gases to make water is an exothermic reaction as it releases energy as new bonds are formed.
What is an exothermic reaction?An exothermic reaction is defined as a chemical reaction which involves release of energy in the form of light,heat .In these reactions, energy is transferred from system to surroundings rather than taking energy from surroundings into system as in endothermic reactions.
In an exothermic reaction,change in enthalpy is negative.Therefore, it can be inferred that net amount of energy which is required to start the exothermic reaction is less than the net amount which is released by the reaction.
Examples of exothermic reactions are combustion reactions, detonation of nitroglycerin , neutralization reactions and nuclear fission.
Learn more about exothermic reactions,here:
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The recommended dose of aminophylline for children is 1.0 mg/kg/hr. 15 mL of a 30 mg/mL sltn is added to a 150 mL bottle of D5W. At what rate mL/hr should the injection be delivered to 35 lb child
Answer:
The answer is "6.68 [tex]\frac{ml} {hr}[/tex]".
Explanation:
It's going to be 18.18 kg to turn body mass to kg.
Size 1mg / kg / hr, therefore = 1 x 18.18
= 18.18 kg / hr
now we adding 30 mg / ml of dextrose = 30 x 15
[tex]=\frac{450mg}{15 ml +150 ml}[/tex]
of dextrose, from 15 ml to 150 ml;
Therefore, now 450 mg in 165m:
[tex]= \frac{ 450}{165}\\ \\=2.72 \frac{mg} {ml}[/tex]
now divide the 18.18 by 2.72:
[tex]=\frac{18.18}{2.72}[/tex]
= 6.68 [tex]\frac{ml} {hr}[/tex]
3.87 moles of iron bromide yielded10.4 moles of sodium bromide
Answer: 89.57 %
Hope it helps
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
Balance the following equation. Choose "blank" if no coefficient other than 1 is needed. CaCl2 + Na2CO3 CaCO3 + NaCl
Answer:
Hi there!!!
The answer is given in picture.
In question we had 2 sodium(Na) and chlorine (cl) but after reaction nacl donot contain it. so, we need to put 2 infront of nacl to make them equal.
As balancing chemical equation refers to the process of keeping or making equal to the atoms of both product and reactant.
Hope it helps..
explain the formation of coke?
please answer this question
I will mark u the brainlest☺️☺️
Answer:
Here is it....
Explanation:
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.
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]
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.
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.
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 :)
What is the atomic number of neon?
Answer:
the atomic number of a neon is 10
