Is Matter Around Us Pure? — Science STD 9 — Question

In the atom of an element X, 6 electrons are present in the outermost shell. If it acquires noble gas configuration by accepting requisite number of electrons, then what would be the charge on the ion so formed?

The solubility of ammonium chloride in water at various temperatures is given below:

Temperature:	10°C	20°C	40°C	60°C	80°C
Solubility:	24g	37g	41g	55g	66g

What mass of ammonium chloride whould be needed to make a saturated solution of ammonium chloride in fifty grams of water at 40°C?

Classify the following into elements, compounds and mixtures:
Marble, Air, Gold, Brass, Sand, Diamond, Graphite, Petroleum, Common salt, Sea-water, chalk.

If one mole of nitrogen molecules weights 28g, calculate the mass of one molecule of nitrogen in grams.

Why the symbols of few elements, like sodium, do not start with the initial letter of the name?

Why does water have higher boiling point than alcohol? At what temperature in Kelvin, it can be changed into solid state and into vapours?

Name two solid, two liquids and two gaseous elements at the room temperature.

If an atom contains one electron and one proton, will it carry any charge or not?

Explain the formation of (i) sodium ion, and (ii) chloride ion, form their respective atoms giving the number of protons and number of electrons in each one of them. What is the reason for positive charge on a sodium ion and a negative charge on a chloride ion?

A 0.24g sample of compound of oxygen and boron was found by analysis to contain 0.096g of boron and 0.144g of oxygen. Calculate the percentage composition of the compound by weight.