Carbon and its Compounds — Science STD 10 — Question

Nitrogen (atomic number 7) and phosphorus (atomic number 15) belong to group 15 of the periodic table. Write the electronic configurations of these two elements. Which of these will be more electronegative? Why?

An object is placed at a distance of 6cm from a convex mirror of focal length 12cm. Find the position and nature of the image.

How does the light have to enter the glass:

1. To produce a large amount of bending?
2. For no refraction to happen?

Write the balanced chemical equations for the following reaction.
Sodium carbonate on reaction with hydrochloric acid in equal molar concentrations gives sodium chloride and sodium hydrogencarbonate.

A convex lens of focal length 25cm and a concave lens of focal length 10cm are placed in close focal contact with each other. Calculate the lens power of this combination.

When a solution becomes more acidic, pH gets lower.

State Mendeleev’s periodic law.

Metals X and Y can be recovered from the anode mud left behind after the electrolytic refining of copper metal. The coins made of metal X look new even after several years of use but the coins made of metal Y lose their shine gradually and get blackened soon. When metal X is alloyed with a small amount of metal Y, it becomes hard and hence suitable for making ornaments. What are metals X and Y ? Also state the colour of metal X.

The diagram given alongside shows a ray of light entering a rectangular block of glass:

1. Copy the diagram and draw the normal at the point of entry.
2. Draw the approximate path of the ray of light through the glass block and out of the other side.

What is a group in the periodic table? In which part of a group would you separately expect the elements to have.

1. The greatest metallic character.
2. The largest atomic size?