Polycrystalline crucible factory calendar

(1) sodium bicarbonate is decomposed into sodium carbonate, water and carbon dioxide at about 270℃, and the reaction equation is 2NaHCO3═? △? . ? Sodium carbonate +H2O+ carbon dioxide =

So the answer is: 2NaHCO3? △? . ? Sodium carbonate +H2O+ carbon dioxide =

② Take out the hot crucible with crucible pliers. Sodium carbonate absorbs water easily, so it should be cooled in a dryer.

Therefore, the answer is: crucible pliers; C.

(3) The difference of solid mass before and after the reaction can indicate that the mass of generated steam and carbon dioxide gas is (mm 1-mm2)g, and the mass of sodium bicarbonate in the sample is a, then:

2NaHCO3？ △? . ? Sodium carbonate +H2O+ carbon dioxide = Solid mass decreases by △m

2×84g？ 62g

Answer? （m 1-m2）g

Solution: a = 2×84g×(m 1? m2）g62g = 84（m 1？ M2)3 1 g

Therefore, the mass fraction of sodium bicarbonate in the sample is 84(m 1? m2）3 1g（m 1？ a）g× 100% = 84（m 1m2）3 1（m 1a）× 100%。

So the answer is: 84(m 1? m2）3 1（m 1a）× 100%。

(4) Let the mass of the sample be X, then the mass of sodium bicarbonate is 90% X. If the value of (m 1-m2) in this question exceeds 0.6g, that is, the mass of steam and carbon dioxide gas generated exceeds 0.6g, the minimum value is 0.6g first, and then:

2NaHCO3？ △? . ? Sodium carbonate +H2O+ carbon dioxide = Solid mass decreases by △m

2×84g？ 62g

90%X？ 0.6 g

So 90%X2×84g=0.6g62g, and the solution is x =1.8g..

Answer: At least weigh the sample1.8g..