Question

16 (a) Define the Law of definite proportions.
(b) Calculate the number of Moles in 52 g of He (atomic mass of He is 4u).
(0) How many atoms are present in one mole of a substance?
17(a) Name two cell organelles that have their own DNA. M
P
(b) Mention the function of lysosomes.
(o
pand DNA and mention its function.
18. A body of mass 5kg is moving with a velocity of 20m/s. A force is applied on the body for 25s and it
attains a velocity of 40m/s. What is the force applied?
OR
Calculate the force required to impart a velocity of 30m/s in 10s to a car initially at rest on a horizontal
smooth surface. The mass of the car is 1500kg.​

Answer 1

GIVEN :-

• m = 5kg

• u = 20m/s

• v = 40m/s

• t = 25s

Solution :-

We know that,

==> a = (v-u) /t

==> a = ( 40-20)/25

==> a = 20/25

==> a = 0.8m/s²

NOW,

==> F = ma

==> F = 5 × 0.8

==> F = 4N.

or

GIVEN :-

• m = 1500kg

• t = 10s

• v = 30m/s

Solution :-

We know that,

==> v +u = t

==> 30 +u = 10

==>.°. u = 20m/s

==> .°. a = (v-u) /t

==> a = ( 30-20)/10

==> a = 1m/s²

NOW,

==> F = ma

==> F = 1500 × 1

==> F = 1500N

Answer 2

Answer:

16)a) A given chemical substance always contains the same elements combined in a fixed proportion by weight. This law was proposed by JOSEPH PROUST

b)w=52g

atomic mass(m)= 4

no. of moles=w/m

=52/4

=13 moles

c)One mole (abbreviated mol) is equal to 6.022×1023 molecular entities (Avogadro's number), and each element has a different molar mass depending on the weight of 6.022×1023 of its atoms (1 mole).

17)a)Mitochondria and chloroplasts are the only two organelles of animal and plant cells that contain their own DNA.

17)b)Inside a cell, numerous organelles function to remove wastes. One of the key organelles involved in digestion and waste removal is the lysosome. Lysosomes are organelles that contain digestive enzymes. They digest excess or worn out organelles, food particles, and engulfed viruses or bacteria

17)c)DNA-Deoxyribonucleic acid

The four roles DNA plays are replication, encoding information, mutation/recombination and gene expression.

1.Replication. DNA exists in a double-helical arrangement, in which each base along one strand binds to a complementary base on the other strand. ...

2.Encoding Information. ...

3.Mutation and Recombination. ...

4.Gene Expression.

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