Science - NCERT Solutions - GeniusJnr

To show that zinc is a more active metal than copper, the correct procedure is to: 

(1) add dilute nitric acid on strips of both the metals. 

(2) observe transmission of heat through strips of zinc and copper. 

(3) prepare solution of zinc sulphate and hang strip of copper into it. 

(4) prepare solution of copper sulphate and hang strip of zinc into it. 

A parachutist is descending vertically and makes angles of elevation of 45° and 60° at two observing points 100 m apart from each other on the left side of himself. Find the maximum height from which he falls and the distance of the point where he falls on the ground form the just observation point.

Use the following information to answer the next question.

Manganese dioxide reacts with aluminium to produce manganese and aluminium oxide. The chemical equation involved in the reaction can be represented as: $3{\mathrm{MnO}}_{2 }\left(\mathrm{s}\right)+ 4\mathrm{Al} \left(\mathrm{s}\right) \to 3\mathrm{Mn} \left(\mathrm{s}\right) + 2{\mathrm{Al}}_2{\mathrm{O}}_{3 }\left(\mathrm{s}\right)+\mathrm{Heat}$ In the above reaction, is oxidized and is reduced. It is an example of anreaction.

The information in which alternative completes the given statements?

Which of the following equations represents a single displacement reaction?

Use the following information to answer the next question.

Zinc oxide reacts with carbon to produce zinc and carbon monoxide. The balanced chemical equation for the given reaction can be represented as: $\mathrm{ZnO} \left(\mathrm{s}\right) + \mathrm{C} \left(\mathrm{s}\right) \to \mathrm{Zn} \left(\mathrm{s}\right) + \mathrm{CO} \left(\mathrm{g}\right)$

Which of the following substances is oxidized in the given reaction?

Which chemical formula represents bleaching powder?

Use the following information to answer the next question.

The general chemical equation for a displacement reaction can be written as:  A + Salt solution of B → Salt solution of A + B

The elements that A and B respectively represent are

The number of times a particular item occurs in a given data is called its

(a) variation

(b) frequency

(c) cumulative frequency

(d) class-size

The difference between the upper and the lower class limits is called

(a) mid-points

(b) class size

(c) frequency

(d) mean

Following are the ages of 360 patients getting medical treatment in a hospital on a day:
 
Construct a cumulative frequency distribution.

Use the following information to answer the next question.

Lead nitrate [Pb(NO3)2], on heating, undergoes decomposition reaction to give lead oxide (PbO), nitrogen dioxide (NO2), and oxygen (O2) according to the following chemical equation.

The information in which alternative contains the correct values of the coefficients for the given equation?

Use the following information to answer the next question.

Metal X undergoes the following reaction with the salt solution of metal Y. Metal X + Salt solution of Y → Salt solution of X + Metal Y

The metals X and Y respectively are likely to be