Tag: chemistry

Questions Related to chemistry

The boiling point of water on the Kelvin scale is:

chemistry matter around us measurement of properties effect of temperature and pressure on states of matter general introduction: importance and scope of chemistry

  1. $373.15 K$

  2. $273.15 K$

  3. $373 K$

  4. $374.15 K$

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Correct Option: A
Explanation:
The boiling point of a substance is the temperature at which the liquid changes into a vapor.
Boiling point of water is $100^0C$

To convert kelvin scale, we have to add 273.15 to $^0C$ scale value
So,
$100^0C=100+273.15=373.15K$

Hence, option $A$ is correct.

Which temperature scale is the primary unit of measurement and analysis in the physical world?

chemistry matter around us measurement of properties effect of temperature and pressure on states of matter general introduction: importance and scope of chemistry

  1. Celsius Scale

  2. Kelvin Scale

  3. Fahrenheit Scale

  4. None of these

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Correct Option: B
Explanation:
The kelvin is a unit of measure for temperature based upon an absolute scale. It is one of the seven base units in the International System of Units (SI) and is assigned the unit symbol K.
The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all thermal motion ceases in the classical description of thermodynamics. 
The correct answer is B.

What temperature scale must always be used when working gas law problems?

chemistry matter around us measurement of properties effect of temperature and pressure on states of matter general introduction: importance and scope of chemistry

  1. Celsius Scale

  2. Kelvin Scale

  3. Rankine Scale

  4. Fahrenheit scale

Show answer
Correct Option: B
Explanation:
You should always use the Kelvin scale to measure temperatures of gases for use with the gas laws. 
Imagine you have a gas at 1$^0C$ and it is heated to $2^0C$. Just using Celsius temperatures you have doubled the temperature when in reality the amount of additional kinetic energy of a gas at $2^0C$ is only slightly higher than a gas at $1^0C.$
Also, imagine working a problem where you would need to divide by a temperature of $0^0C$. Wouldn't work! You have the same issue at $0K$, but since the material would not be a gas at $0K$ it is not an issue.
So we use kelvin scale always in gas problems.Option B is correct.

Kelvin scale has:

chemistry matter around us measurement of properties effect of temperature and pressure on states of matter general introduction: importance and scope of chemistry

  1. no fixed points

  2. one fixed point.

  3. two fixed points

  4. none of these

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Correct Option: C
Explanation:

In Kelvin scale, temperature is expressed in Kelvin. In SI system, Kelvin is the unit of temperature. In this scale of temperature, zero of the scale corresponds to $-273^0C$, which is said to be the temperature at which the volume of a gas reduces to zero. Hence, $-273^0C$ is also known as the absolute zero. For the same reason, this scale of temperature is also known as absolute scale of temperature. On this scale, the lower fixed point i.e. the temperature of melting ice at normal pressure is +273K and the upper fixed point i.e. the temperature of boiling water at normal pressure is 373K. 

Which of the following are incorrect SI units?

chemistry matter around us measurement of properties effect of temperature and pressure on states of matter general introduction: importance and scope of chemistry

  1. Amount of substance in mol L$^{-1}$

  2. Pressure of gas in pascal

  3. Density of a solid in kg m$^{-3}$

  4. Force in newton

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Correct Option: A
Explanation:

The SI units is based on seven base units. These are metre, kilogram, second, ampere, kelvin, mole and candela.

Here Pascal is SI unit of pressure
Newton is unit of force

Amount of substance has a SI unit $mol/ m^3$
Option A is the incorrect SI Unit.

One gram of mass is equal to:

chemistry matter around us measurement of properties effect of temperature and pressure on states of matter general introduction: importance and scope of chemistry

  1. $5\times { 10 }^{ 10 }erg$

  2. $9\times { 10 }^{ 20 }erg$

  3. $7\times { 10 }^{ 5 }erg$

  4. $11\times { 10 }^{ 12 }erg$

Show answer
Correct Option: B
Explanation:

$E=mc^2$

$E=1\ g \times (3\times 10^{10}\ cm/s)^2 $
$=9\times 10^{20}\ erg$

Which of the following relationships are wrong?

chemistry matter around us measurement of properties effect of temperature and pressure on states of matter general introduction: importance and scope of chemistry

  1. $1 \,atm\approx 0.1 \, bar$

  2. $1 \,liter= 1 \, dm^3$

  3. $1\, J =0.239 \, cal$

  4. $1\, eV =9.11 \times 10^{-4} J$

Show answer
Correct Option: A,D
Explanation:

$1\quad atm=1.01325\quad bar\approx 1\quad bar\neq 0.1\quad bar$

$1\quad litre={ 10 }^{ -3 }{ m }^{ 3 }=1{ dm }^{ 3 }$
$1\quad cal =4.18\quad J \Rightarrow 1\quad J =0.239\quad cal\ 1\quad ev=1.6\times { 10 }^{ -19 }J \neq  9.11\times { 10 }^{ -4 }J$
Therefore, $(A). (D)$ are the correct answer.

Units of physical quantities can be expressed in terms of fundamental units and such units are called:

chemistry matter around us measurement of properties effect of temperature and pressure on states of matter general introduction: importance and scope of chemistry

  1. Fundamental units

  2. Derived units

  3. Both a and b

  4. None of the above

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Correct Option: B
Explanation:

Units of physical quantities can be expressed in terms of fundamental units and such units are called $\text{derived units}$. 

Unit of area can be an example for derived unit. If $L$ is the length of the square then $L \times L$ is $L^{2}$ is its area. Hence, option A is correct.

The units of fundamental physical quantities are called

chemistry matter around us measurement of properties effect of temperature and pressure on states of matter general introduction: importance and scope of chemistry

  1. Fundamental units

  2. Derived units

  3. Both a and b

  4. None of the above

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Correct Option: A
Explanation:

The units of fundamental physical quantities are called fundamental units. They are length, mass and time.
Hence option A is correct.

Match the following combinations of electrical units with their terms as single unit:

Electrical unit Single unit
(I) ampere-second A. coulomb
(II) volt-ampere B. ohm
(III) volt-ampere$^{-1}$ C. ampere
(IV) walt/ampere ohm D. watt
(V) joule / ampere second E. volt
chemistry matter around us measurement of properties effect of temperature and pressure on states of matter general introduction: importance and scope of chemistry

  1. A- I B-III C-IV D-II E-V

  2. A- I B-II C-III D-IV E-V

  3. A- V B-IV C-III D-II E-I

  4. A- I B-V C-IV D-II E-III

Show answer
Correct Option: A
Explanation:

Electrical unit     Single unit

(I) ampere-second                   coulomb

(II) volt-ampere                         Ampere

(III) volt-ampere$^{-1}$         Volt

(IV) walt/ampere ohm              Ohm

(V) joule / ampere second       Volt

So correct options are A- I B-III C-IV D-II E-V

Hence option A is correct.