Metals and Non-Metals — Science STD 10 — Question

What were the limitations of Dobereiner’s classification of elements?

It is possible to replace resistors joined in series by an equivalent single resistor of resistance. How?

When a metal X is treated with cold water, it gives a basic salt Y with molecular formula XOH (Molecular mass = 40) and liberates a gas Z which easily catches fire. Identify X, Y and Z and also write the reaction involved.

The electronic configurations of three elements X, Y and Z are as follows:
X 2, 4
Y 2, 1
Z 2, 1

1. Which two elements will combine to form an ionic compound?
2. Which two elements will react to form a covalent compound?

Give reasons for your choice.

Give reasons:
Use of a mild base like baking soda provides relief on the area stung by honeybee.

The calorific values of three fuels A, B and C are 33kJ/ g, 48kJ/ g and 150kJ/ g, respectively. A is solid, B is liquid and C is a gas at room temperature. One combustion, both A and B produce carbon dioxide while C explodes forming steam. B and C leave no residue after combustion while A leaves behind some solid residue. Which one of the three fuels is the most ideal? Give two reasons to support your answer.

What type of bonding would you expect between the following pairs of elements?

1. Calcium and Oxygen.
2. Carbon and Chlorine.
3. Hydrogen and Chlorine.

List six specific characteristics of sexual reproduction.

What are the limitations of extracting energy from

1. the wind?
2. waves?
3. tides?