NDA CHEMISTRY SECTIONAL TEST

Question 1:

DIRECTIONS: Read the following two statements and choose the correct answer.

Statement 1 – Empirical formula mass of ethene is equal to nitrogen

Statement 2- Empirical formula mass is twice the molecular formula mass

Statement 1 is correct but 2 is incorrect

Statement 2 is correct but 1 is incorrect

Both statements are correct and statement 2 is the correct explanation of statement 1

Both statements are correct and statement 2 is the not the correct explanation of statement 1

Question 2:

The normal concentration of citric acid when 25.00 mL citric acid solution is titrated with 28.12 mL of 0.1718 N KOH solution is

0.1200 N

0.1932 N

0.2342 N

0.2534 N

Question 3:

The equivalent weight of H₃PO₂ , when it disproportionate into PH₃ and H₃PO₃is

M

M/2

3M/4

2M

Question 4:

If 700 mL of H₂ at STP contains x molecules of it, how many molecules of O₂ are present in 700 mL of it at the same temperature and pressure?

x

2x

3x

4x

Question 5:

In a reaction A + B₂ ----> AB₂, 400 atoms of A reacts with 200 molecules of B. The limiting reagent is

A

B₂

AB₂

No limiting reagent

Question 6:

Calculate the elemental atomic mass of Mg if the naturally occurring isotopes are ²⁴Mg, ²⁵Mg and ²⁶Mg. Their masses and abundances are as follows:

Isotope	Atomic Mass	Isotopic Abundance
²⁴Mg	23.98504 u	78.70%
²⁵Mg	24.98584 u	10.13%
²⁶Mg	25.98259 u	11.17%

24.31 u

25.65 u

23.31 u

20.98 u

Question 7:

Two containers of equal capacity A1 and A2 contain 10 g of oxygen (O₂) and ozone (O₃) respectively. Which of the following statement is correct ?

A1 and A2 have same number of atoms , A1 contain more number of molecules

A1 and A2 have same number of atoms , A2 contain more number of molecules

A1 and A2 have different number of atoms , A1 contain more number of molecules

A1 and A2 have different number of atoms , A2 contain more number of molecules

Question 8:

How many molecules approximately do you expect to be present in a small crystal of sugar which weighs 10 mg?

1.90 × 10¹⁹ molecules

1.98 × 10¹⁹ molecules

1.86 × 10¹⁹ molecules

1.76 × 10¹⁹ molecules

Question 9:

A solution contains 25% water,25% ethyl alcohol and 50% acetic acid by mass .The mole fraction of water is

0.6

0.7

0.5

0.2

Question 10:

A sample of nitric acid is 69% by mass and it has a concentration of 15.44 mol/L. Its density is-

1.42 g/cc

1.62 g/cc

1.75 g/cc

2.57 g/cc

Question 11:

Mass of urea (NH₂CONH₂) required in making 1.5 kg of 0.20 molal aqueous solution is-

18 g

20 g

19g

17g

Question 12:

Three compounds A, B and C are formed when carbon combines with hydrogen. The percentage of hydrogen in A, B, and C are 25, 14.3, and 7.7 respectively. The empirical formulae of the compounds A , B and C are

CH₄ , CH₂ , CH₅

CH₄ , CH₂ , CH

CH₄ , CH₂ , CH₂

CH₄ , CH₂ , CH₃

Question 13:

A solution is prepared by dissolving 15 g of cane sugar in 60 g of water. The mass percent of cane sugar and water are

20% , 80%

25% , 65%

80% , 20%

75% , 25%

Question 14:

Molecules are there in 10.0 liters of a gas at a pressure of 75 cm at 27°C is

1.409 × 10²³ molecules

4.409 × 10²³ molecules

2.409 × 10²³ molecules

3.409 × 10²³ molecules

Question 15:

Which of the following scientist is the first one to propose the model of an atom ?

Rutherford

J.J Thomson

Neil Bohr

Both 2 and 3

Question 16:

Gold foil is selected by Rutherford model of an atom because

Gold is most malleable metal
Gold was about 1000 atoms thick
Gold is most ductile metal
Gold is least reactive metal

Both 1 and 2

Both 2 and 4

Both 1 and 4

Both 2 and 3

Question 17:

Limiting reagent is

The reactant that is used up first and limits the amount of product formed .

The reactant that is used up last and limits the amount of product formed.

The reactant that makes the product.

The substance that is in excess that doesn't get used up as a reactant.

Question 18:

6 mg of mercury was found in a 5 L sample of water. What is the concentration (molarity) of mercury in ppm? (Atomic mass of mercury = 200 g / mol)

1.2 ppm

6000 ppm

600 ppm

6 ppm

Question 19:

Which of the following is not the postulates of the Thomson model of an atom ?

An atom consists of a positively charged sphere and the electrons are revolving .

The negative and positive charges are equal in magnitude.

Thomson’s model was not able to explain that atoms are electrically neutral.

Both 1 and 4

Question 20:

5 g of methyl alcohol is present in 100 mL of solution. If the density of solution is 0.96 g/mL . The mass percentage of methyl alcohol solution is

16.54 %

15.62 %

17.56 %

11.24 %

NDA CHEMISTRY SECTIONAL TEST - 2

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आइसोटोप	परमाणु भार	समस्थानिक बहुतायत
²⁴Mg	23.98504 u	78.70%
²⁵Mg	24.98584 u	10.13%
²⁶Mg	25.98259 u	11.17%

NDA CHEMISTRY SECTIONAL TEST - 2

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