Science (SIQ)

Zinc liberates hydrogen gas when reacted with dilute hydrochloric acid, whereas copper does not. Explain why? 

Ans. 

(i) Zinc reacts with hydrochloric acid to liberate Hydrogen gas as Zn is more reactive than Hydrogen and hence, displace it. 

Copper is less reactive then Hydrogen and hence cannot displace it.
Hence, Zinc liberates hydrogen gas when reacts with dilute hydrochloric acid, whereas copper does not.

Zn>H>Cu

(ii) to avoid the photochemical reaction the silver chloride is placed in dark coloured bottles.

what happens when Bleaching powder is left exposed to air

Ca(OH)2+Cl2 → CaOCl2 

bleaching powder is kept open in air. ... If bleaching powder is held exposed in the air, it reacts with carbon dioxide (CO2) from the atmosphere to produce calcium carbonate (CaCO3) and chlorine gas (Cl2).

Q. A metal 'X' combines with a non-metal 'y' by the transfer of electrons to form a compound Z.  

(i) State the type of bond in compound Z.  

(ii) What can you say about the melting point and boiling point of compound Z?  

(iii) Will this compound dissolve in kerosene or petrol?  

(iv) Will this compound be a good conductor of electricity?

Ans. 

(i) Ionic Bond 

(ii) High 

(iii) No 

(iv) Yes

Q  An element placed in the 2nd group and third period of the periodic table burns in the presence of oxygen to form a basic oxide. 

(a)identify the element

(b)write the electronic configuration 

(c)write a balanced equation when it burns in the presence of air 

(d)write a balanced equation when this oxide is dissolved in water

(e)draw electron dot structure for the formation of this oxide ​

ANSWER

(a) Magnesium 
(b)  2, 8, 2 
(c) 2Mg+O2​→2MgO
(d) MgO+H2​O→Mg(OH)2​
(e) Electron dot structure for the formation of magnesium oxide is shown in image: 

Zinc liberates hydrogen gas when reacted with dilute hydrochloric acid, whereas copper does not. Explain why? 

sport formation in rhizopus

Q28.Mendel crossed a pea plant having round green seeds with pea plant havingwrinkled yellow seeds.
(I) What type of cross is it?
(1) What type of plant are obtained in F1 generation?
(ili) in F2 generation, the phenotype ratio is 9:3:3:1,
State the rule of inheritance of traits as observed by MMendel

(i) monohybrid

(ii) heterogeneous round green

(iii). 

Question 11. Describe double circulation in human beings. Why is it necessary?

Ans. During the blood circulation the blood goes twice in the heart do it is known as double circulation. 

It is necessary in human being to separate the oxygenated and de-oxygenated blood, this is also helps in maintaining the body temperature.

should the resistance of an ammeter be high or low give reason

The resistance of an ammeter should be low. An ammeter has to be connected in series with the circuit to measure current. 

because in series they measure the current passing through them so low resistance helps ammeter to detect the accurate value of current.

so we can say Ammeter should have low resistance so that it doesn't change the main current in the circuit

How does carbon attain noble gas configuration ?ANSWER

Carbon has four electrons in its valence shell. So, it can neither accept nor gain four-electron. One way to complete octet is by sharing of electrons. So, carbon forms a covalent bond to complete its octet.

Is the position of a star as seen by us its true position? Give reasons for your answer.

ANSWER

No, it is not true position. 

due to the atmospheric refraction the star scene higher than actual position in the sky.

We know there are many layers in atmosphere, therefore light coming from stars undergo  many refraction which occurs in gradually changing refractive index of medium and therefore we see the apparent position of the star.

 In a series electrical circuit comprising a resistor made up of a metallic wire, the ammeter reads 5 A. What is the reading of the ammeter when the length of the wire is doubled ?

The resistance (R) is directly proportional to the length of the conductor, when the length is increased the resistance increases and the current decreases.

The current through the circuit is 5A. 

That is, 

I=RV​=5A.

As the resistance is proportional to length, when the length is doubled, the resistance is also doubled. 

That is, I′=2RV​=2.5A. 

Hence, the reading in the ammeter is half when the length of the conductor is doubled.