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2 years ago

Classify the sentences based on the chemical reactions they describe.

1 answer:

5 0

1.When a clam shell (CaCO3) is heated,carbon dioxide (CO2) is given off and a white powder, calcium oxide (CaO), forms.
This is a decomposition reaction because calm shell CaCO3 is getting decomposed into other products.

2.'Nitrogen pentoxide (N2O5) is an unstable gas that changes to nitrogen dioxide (NO2) and oxygen (O2) at room temperature.
This is also a decomposition reaction as nitrogen pentaoxide is getting decomposed.

3.Sodium (Na) reacts with chlorine (Cl) to give sodium chloride (NaCl).
This is a synthesis reaction as two reactants are producing a product.

4.Zinc (Zn) metal reacts with copper sulfate (Cu2SO4) to give zinc
sulfate (ZnSO4) and copper (Cu).
This is a displacement reaction because Zn displaces Cu.

5.A strip of magnesium (Mg) burns brightly in oxygen (O2) to form a white powder, magnesium oxide (MgO).
This is a synthesis reaction because Mg and oxygen react to form magnesy oxide.

6.On heating iron ore (Fe2O3) with carbon (C), we get iron (Fe) and carbon dioxide (CO2).
This is a synthesis reaction because iron oxide reacts with carbon to produce Fe.

You might be interested in

Which one of the equations below is an exothermic reaction?

Yuri [45]

Answer:

B) CaO(s) + H2O(l) --> Ca(OH)2(aq)

Explanation:

This is the only reaction with a negative enthalpy value. Exothermic reactions have a negative enthalpy.

3 0

2 years ago

An unknown salt is either NaF, NaCl, or NaOCl. When 0.050 mol of the salt is dissolved in water to form 0.500 L of solution, the

victus00 [196]

Answer: The unknown salt is NaF

Explanation:

To calculate the molarity of solution, we use the equation:

$\text{Molarity of the solution}=\frac{\text{Moles of solute}}{\text{Volume of solution (in L)}}$

Moles of salt = 0.050 moles

Volume of solution = 0.500 L

Putting values in above equation, we get:

$\text{Molarity of salt}=\frac{0.050mol}{0.500L}\\\\\text{Molarity of salt}=0.1M$

To calculate the hydroxide ion concentration, we first calculate pOH of the solution, which is:

pH + pOH = 14

We are given:

pH = 8.08

$pOH=14-8.08=5.92$

To calculate pOH of the solution, we use the equation:

$pOH=-\log[OH^-]$

Putting values in above equation, we get:

$5.92=-\log[OH^-]$

$[OH^-]=10^{-5.92}=1.202\times 10^{-6}M$

The unknown salt given are formed by the combination of weak acid and strong acid which is NaOH

The chemical equation for the hydrolysis of $X^-$ ions follows:

$X^-(aq.)+H_2O(l)\rightleftharpoons HX(aq.)+OH^-(aq.);K_b$

Initial: 0.1

At eqllm: 0.1-x x x

Concentration of $OH^-=x=1.202\times 10^{-6}M$

The expression of $K_b$ for above equation follows:

$K_b=\frac{[OH^-][HX]}{[X^-]}$

Putting values in above expression, we get:

$K_b=\frac{(1.202\times 10^{-6})\times (1.202\times 10^{-6})}{(1-(1.202\times 10^{-6}))}\\\\K_b=1.445\times 10^{-11}M$

To calculate the acid dissociation constant for the given base dissociation constant, we use the equation:

$K_w=K_b\times K_a$

where,

$K_w$ = Ionic product of water = $10^{-14}$

$K_a$ = Acid dissociation constant

$K_b$ = Base dissociation constant = $1.445\times 10^{-11}$

Putting values in above equation, we get:

$10^{-14}=1.445\times 10^{-11}\times K_a\\\\K_a=\frac{10^{-14}}{1.445\times 10^{-11}}=6.92\times 10^{-4}$

We know that:

$K_a\text{ for HF}=6.8\times 10^{-6}$

$K_a\text{ for HCl}=1.3\times 10^{6}$

$K_a\text{ for HClO}=3.0\times 10^{-8}$

So, the calculated $K_a$ is approximately equal to the $K_a$ of HF

Hence, the unknown salt is NaF

6 0

2 years ago

How many inner, outer, and valence electrons are present in an atom of each of the following elements?

Aneli [31]

Answer:

For a: The number of inner electrons, outer electrons and valence electrons are 28, 7 and 7 respectively.

For b: The number of inner electrons, outer electrons and valence electrons are 54, 1 and 1 respectively.

For c: The number of inner electrons, outer electrons and valence electrons are 23, 1 and 1 respectively.

For d: The number of inner electrons, outer electrons and valence electrons are 36, 2 and 2 respectively.

For e: The number of inner electrons, outer electrons and valence electrons are 2, 7 and 7 respectively.

Explanation:

Outer shell electrons are the electrons which are not tightly held by the electrons. They are called as valence electrons. The electrons present in the highest principle quantum number are known as valence electrons.

Inner shell electrons are the electrons which are tightly held by the electrons. They are called as core electrons.

Inner electrons = Total number of electrons - Valence electrons

Total number of electrons in an atom is equal to the atomic number of the element.

For the given options:

Option a: Bromine (Br)

Bromine is the 35th element of the periodic table having electronic configuration of $1s^22s^22p^63s^23p^64s^23d^{10}4p^5$

Highest principle quantum number is 4

Number of valence electrons = 7

Number of outer electrons = 7

Number of inner electrons = 35 - 7 = 28

Option b: Cesium (Cs)

Cesium is the 55th element of the periodic table having electronic configuration of $1s^22s^22p^63s^23p^64s^23d^{10}4p^65s^24d^{10}5p^66s^1$

Highest principle quantum number is 6

Number of valence electrons = 1

Number of outer electrons = 1

Number of inner electrons = 55 - 1 = 54

Option c: Chromium (Cr)

Chromium is the 24th element of the periodic table having electronic configuration of $1s^22s^22p^63s^23p^64s^13d^{5}$

Highest principle quantum number is 4

Number of valence electrons = 1

Number of outer electrons = 1

Number of inner electrons = 24 - 1 = 23

Option d: Strontium (Sr)

Strontium is the 38th element of the periodic table having electronic configuration of $1s^22s^22p^63s^23p^64s^23d^{10}4p^65s^2$

Highest principle quantum number is 5

Number of valence electrons = 2

Number of outer electrons = 2

Number of inner electrons = 38 - 2 = 36

Option e: Fluorine (F)

Fluorine is the 9th element of the periodic table having electronic configuration of $1s^22s^22p^5$

Highest principle quantum number is 2

Number of valence electrons = 7

Number of outer electrons = 7

Number of inner electrons = 9 - 7 = 2

4 0

2 years ago

The student collects the H2(g) produced by the reaction and measures its volume over water at 298 K after carefully equalizing t

lubasha [3.4K]

Answer:

The pressure of H₂(g) = 741 torr

Explanation:

Given that:

The atmospheric pressure measured in the lab = 765 torr

The vapor pressure of water = 24 torr

By applying Dalton's Law of Partial Pressure :

$P_{total} = P_{H_2}+P_{H_2O}$

Making The Pressure inside the tube due to the H₂(g) the subject of the formula :

we have:

$P_{H_2} = P_{total} - P_{H_2O}$

= (765 -24) torr

= 741 torr

Therefore; the pressure of H₂(g) = 741 torr

4 0

2 years ago

David has two containers of two different gases at the same temperature and pressure. David could assume all of following EXCEPT

pychu [463]

Answer:

David could not assume that:

 when the pressure is decreased, the temperature of both containers will increase (option D).

Explanation:

Since this question has only one answer, you must assume that both containers are identical, i.e. have the same volume.

Using the ideal gas equation pV = nRT you can conclude that pressure and temperature are directly related, i.e. if the pressure is decreased, the temperature will decrease proportionally, which is opposite to the assumption that when the pressure is decreased, the temperature of both containers will increase.

On the other hand, from the same equation, you can tell the relationship between the other variables and conclude that the other choices are valid assumptions:

A. when the temperature is increased, the volume of both containers will increase:

Correct: pV = nRT shows that volume and temperature are directly related: when T increase, V increase)

B. when the pressure is increased, the volume of both containers will decrease

Correct: pV = nRT shows that p and V and inversely related, so when p is incrased, V will decrease.

C. both containers contain the same number of gas particles

Correct, only if the two containers are identical: since the two containers of the two different gases are at the same temperature and pressure, the equation pV = nRT, shows that if the volumes are equal the number of particles are the same.

3 0

2 years ago