Question

Jena glass is a mixture of:
A) Zinc and barium borosilicates
B) Sodium and iron silicate
C) Sodium and aluminium borosilicates
D) Oxides of the rare earth elements

Answer 1

Hint: Jena glass is a soft glass. It has high resistance towards heat and shock. It is composed of the borosilicates along with the other metals such as zinc, aluminium, magnesium.

Complete answer:
Jena glass is a fine quality glass with improved resistance to heat and shock. It is suited to make chemical glassware.
It was first developed for thermometers and for measuring vessels, optical wares, and scientific and industrial use.
Jena's name is derived from the German word Jenaer Glas. Jena glass was first produced by the German glass chemist Otto Schott.
The earliest Jena glass was a mixture of sodium-magnesium-aluminium-zinc borosilicate which also contains some part of boron trioxide in place of silica.
Jena glass is borosilicate which contains aluminium, magnesium, sodium, and zinc.
It is one of the best glass for scientific purposes. It is composed of barium borosilicate and zinc which produces soft and good quality glass.

Hence, (A) is the correct option.

Additional information:
It is a precursor for the other borosilicate such as a Pyrex. Jena glass is these days known as the borosilicates.
These are used for making of laboratory glassware as they have a very low thermal expansion coefficient $\text{(3}\text{.3 }\!\!\times\!\!\text{ 1}{{\text{0}}^{\text{-6}}}{{\text{K}}^{\text{-1}}}\text{)}$ which one-third of the ordinary soda-lime glass. This reduces the stress on the material which may be caused by the temperature.
They are resistant to thermal shock irrespective of other glasses.
They also exhibit extreme resistance towards the chemically corrosive environment. For example, they are acid and alkali resistant.
On comparing the Jena or borosilicate with the ordinary soda-lime glasses they are less dense due to the low atomic mass of boron. They can withstand before fracturing at about 180 kelvin. This is why they are widely used in kitchen wares or laboratories.

Note:
Apart from borosilicate there are various types of glasses available. Such as soda-lime glass is a very common glass used for various glass materials.