Why the empty crucible should be heated before start the experiment?

Why the empty crucible should be heated before start the experiment?

You must let the crucible cool before measuring it because the heat from the crucible warms the surrounding air, which rises, then that air cools down and falls. This rise and fall of surrounding air is called a convection current and will give you an unsteady reading that is rising and falling.

Why were the crucible and lid heated before obtaining the initial mass?

What is the purpose of preheating the crucible and its lid prior to measuring its mass? cover. The water needs to be driven out prior to the initial massing of the crucible and cover. A student fails to place the lid on the crucible during the initial heating of the hydrated sample and some of the solid spatters out.

What is the purpose of heating your crucible before adding your hydrated salt?

Explain. What is the purpose of firing the crucible? To rid the crucible or sample of any moisture that might be present. A 2.914 g sample of gypsum, a hydrated salt of calcium sulfate (CaSO4) is heated at a temperature greater than 170C in a crucible until a constant mass is reaced.

How should the crucible be heated initially?

After first use — The crucible should be heated to 600°C (1110°F) on low power and then to bright red heat on full power or to the desired temperature, however the slow heating phase to 200°C (390°F) should be adopted whenever the crucible has been allowed to cool off for extended periods.

Why should a crucible be washed before drying it?

The moisture in the desiccator must be allowed to equilibrate with the solid in the weighing bottle. The sintered glass crucible is used to filter the silver chloride precipitate (or other solid) from its parent liquid. Before this crucible can be used for filtering it must be cleaned, then dried to constant weight.

Why is it important to heat the hydrate thoroughly?

It is important to heat the hydrate thoroughly. If the heating is not enough, the water molecules will not be evaporated. There will be some water that is left in the anhydrous form of the hydrate. The amount of water lost is calculated by subtracting the mass of anhydrous from the mass of hydrate.

Why is it important that the crucible be thoroughly dried prior to measuring its mass?

After heating the sample to dryness, you should allow the crucible to cool to room temperature and then immediately measure the mass on a balance. The reason to not let the dried material sit around is because it can re-absorb water from the air upon standing to become a hydrate again.

Why does the mass of a crucible decrease when heated?

If it is hotter the weight will be slightly less, if colder slightly more owing to the production of convection currents which affect the apparent mass.

Why was the crucible heated gently for 5 minutes before intensifying the heat?

why was it important to heat your hydrate gently for 5 min. the crucible cover helps keep the hydrate inside the crucible, and will avoid contaminating the crucible with finger oils.

Why is a hot crucible not weighted?

If a crucible is not at the temperature of the balance compartment it will likely show a weight different from that it would show were it at the same temperature. If it is hotter the weight will be slightly less, if colder slightly more owing to the production of convection currents which affect the apparent mass.

Why should you leave the crucible cover ajar while heating?

While heating the crucible, you must have the lid partially ajar to allow water to escape. You will want a gentle blue flame. Orange flame produces carbon soot which will coat your crucible and alter the weight.

How do you heat in a crucible without cracking it?

Use a soft flame; hot enough to turn the bottom of the crucible orange, but not so hot that you risk cracking the crucible. Turn off your burner and allow the crucible and lid to completely cool to room temperature. You should allow the crucible to cool for at least 15 minutes.