Current location - Recipe Complete Network - Catering industry - (09 Suqian) On June 1 day, 2009, the National Food Safety Law was officially implemented. In the food industry, the word "exemption from inspection" has become history. "All food must be
(09 Suqian) On June 1 day, 2009, the National Food Safety Law was officially implemented. In the food industry, the word "exemption from inspection" has become history. "All food must be
(1) Let the mass of ammonia produced be x.

2NH 3 +H 2 SO 4 ="=" (NH 4 ) 2 SO 4?

34 98?

x? 50g×9.8%? 34/ x? = 98/50g×9.8%? ( 1)

X = 1.7g The mass of ammonia gas is 1.7g? ( 1)

(2)N % =( 1.7g× 14/ 17)/ 100g× 100%? = 1.4%? (2 points)

(3) 1.92% ~ 4% ( 1) ∵ 1.4% ∵ 1.92%? ∴ Milk powder is unqualified? ( 1)

(4) It is assumed that at least yg melamine needs to be added.

100g× 1.4% ﹢y×84/ 126? = (100g-y) ×1.92% (2 points)

y = 0.8g? Add at least 0.8g melamine (1 min).

Analysis: (1) According to the chemical equation of the reaction between ammonia and sulfuric acid, calculate the mass of ammonia from the mass of sulfuric acid consumed by absorbing ammonia;

(2) According to the method of detecting protein, the mass of N element in absorbed ammonia is 100g of milk powder sample, and the calculation can be completed by using the mass fraction of N element in milk powder = × 100%;

(3) According to the average mass fraction of nitrogen in protein is 65438 06%,

Using the mass fraction of nitrogen in milk powder = × 100%, the mass fraction range of nitrogen in milk powder containing protein 12g ~ 25g 100g was calculated. Comparing the mass fraction of N element in the milk powder sample with the national standard to judge whether the milk powder is qualified or not;

(4) After melamine is added to the milk powder, part of the N element comes from protein in the milk powder, and the other part comes from the added melamine. The addition amount is calculated when the mass fraction of N element in the added milk powder reaches the national minimum standard.

Solution: (1) Let the mass of ammonia produced be X.

Ammonium bicarbonate+sulfuric acid/(NH

34 98

x? 50g× 9.8%

x= 1.7g

(2) Nitrogen content in milk powder = × 100%= 1.4%.

(3) Every 100g of milk powder contains protein 12g, and the mass fraction of nitrogen in milk powder = × 100%= 1.92%.

Every 100g of milk powder contains 25g of protein, and the mass fraction of nitrogen in milk powder = × 100%=4%.

The mass fraction of nitrogen in qualified milk powder is 1.92% ~ 4%,

∵ 1.4%< 1.92%

Unqualified milk powder

(4) making the mass of melamine to be added at least Y.

100g× 1.4%﹢y×× 100%=( 100g﹢y)× 1.92%?

y=0.8g

Answer: (1) The mass of ammonia is1.7g; ;

(2) The content of nitrogen in milk powder is 65438 0.4%;

(3) the milk powder is unqualified;

(4) At least 0.8g melamine should be added.