Tag: general introduction: importance and scope of chemistry

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Multiple choice evs look, learn and experience matter: states, classification and properties study of matter general introduction: importance and scope of chemistry

The lightest and the most abundant element in the universe is:

  1. zinc

  2. hydrogen

  3. sodium

  4. mercury
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The lightest and the most abundant element in the universe is hydrogen. The percentage of hydrogen in the universe is more than $91$%.


Therefore, hydrogen is the most abundant element in the universe.

Hence, option B is correct.

Multiple choice evs look, learn and experience matter: states, classification and properties study of matter general introduction: importance and scope of chemistry

Statement 1 : Iron is an element.


Statement 2 : It cannot be broken into smaller units and retain its physical and chemical properties.

  1. <p>

    </p><p>Both Statement 1 and Statement 2 are correct and Statement 2 is the correct explanation of Statement 1</p>

  2. <p>Both Statement 1 and Statement 2 are correct and Statement 2 is not the correct explanation of Statement 1</p>

  3. <p>Statement 1 is correct but Statement 2 is not correct
    </p>

  4. Statement 1 is not correct but Statement 2 is correct

  5. <p>Both the Statement 1 and Statement 2 are not correct</p>
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Iron is an element found in nature as the third most abundant element in the earth's crust.


Element is a pure substance with a single element and cannot be further divided into its constituent elements.

Hence the correct option is A.

Multiple choice evs look, learn and experience matter: states, classification and properties study of matter general introduction: importance and scope of chemistry

True or False.


Baking soda is a compound.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Baking soda is a compound because it's composed of molecules that are all identical. It has the chemical formula $NaHCO _3$ and the chemical name sodium hydrogen carbonate. Pure baking soda is a compound, NaHCO3. But in most cases the white powder will be a mixture between $NaHCO _3$ and $Na _2CO _3$, which resulted after the decomposition of $NaHCO _3$:

$2NaHCO _3 \rightarrow  Na _2CO _3 + CO _2 + H _2O$

Multiple choice evs look, learn and experience matter: states, classification and properties study of matter general introduction: importance and scope of chemistry

In an experiment oxygen was added to hydrogen and heated. On burning a substance containing both oxygen and hydrogen water was formed. What is this substance?

  1. Element

  2. Compound

  3. Solution

  4. Mixture
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Oxygen and hydrogen are two elements and when they react they must generate another compound. Their product is not a mixture and  their result is a different compound with different properties.

Multiple choice evs look, learn and experience matter: states, classification and properties study of matter general introduction: importance and scope of chemistry

The first and last elements of the longest period are ___________.

  1. francium and Uuo

  2. caesium and radon

  3. francium and radon

  4. caesium and Uuo
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Longest period is 6th period. It contains 32 elements. It starts with Caesium. The last element is Radon. 

7th period is not the longest as it contains less than 32 elements.

Multiple choice evs look, learn and experience matter: states, classification and properties study of matter general introduction: importance and scope of chemistry
A, B, C are three elements with atomic numbers, Z-1, Z, and Z+1 respectively. B is an inert gas.
Identify the elements having same valence shell.

  1. A, B

  2. B, C

  3. A, C

  4. A, B, C
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Three elements A,B and C. B is a noble gas, A has atomic number 1 less than B and C has 1 more than B. Hence number of valence shell is same in A and B because on adding one electron to Noble gas that is 18 group next electron will occupy, alkali metals group in a next period hence increases in shell number.