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The key to learning chemistry well is to listen, chemistry can be regarded as a liberal arts in science, and things are very broken. The bareback chemical equation is of little use. Read more books about chemistry, and it's best to do the questions.

a. Lighting an alcohol lamp cannot be lit with a lit alcohol lamp.

Analysis: The landlord's question is the standard operation of the indirect iodometric method. The reaction of potassium dichromate with potassium iodide is generally carried out under acidic conditions (can be dilute sulfuric acid or hydrochloric acid), and h is used in the following reaction equation; In addition, experiments performed after the removal of iodine from the first step of the reaction by heat were used to calibrate the quality of excess potassium dichromate.

Suppose the potassium iodide sample contains potassium iodide x g, potassium dichromate excess y g, and the iodine reacted with sodium thiosulfate during titration has z mol.

k2cr2o7＋6ki＋14h ＝8k ＋2cr3 ＋3i2＋7h2o

y g : z mol

2na2s2o3 ＋ i2＝na2s4o6＋2nai

mol:z mol

z=,y=so the mass of potassium dichromate reacting with this potassium iodide sample is.

6ki＋k2cr2o7＋14h ＝8k ＋2cr3 ＋3i2＋7h2o

x g: x = so the purity of the potassium iodide sample is.

1. 2000*75%*70%=1050t

2.The solution requires a mass of x of hematite

3co+fe2o3=3co2+2fe

x*80% 1600*(1-2%)

160/112=x*80%/1600*(1-2%) x=2800t

3.The quality of hematite required for unraveling is y

3co+fe2o3=3co2+2fe

y*85% 200*(1-3%)

160/112=y*85%/200*(1-3%) y=

Choosing a CA is all about physical change.

b All are chemical changes in spring demolition.

d are all chemical changes (denaturation of proteins).

c There is no chemical reaction in the volatilization of gasoline, which is a physical change; Gasoline is burned to produce carbon dioxide and water, and new substances are formed, which is a chemical change.

a As long as the simplest formula is (co)m (h2)n, it can be completely absorbed after ignition.

A error. First, even if the reaction produces ammonia instead of ammonia, the second is that the types of elements on the two sides are different;

b error. The products of Husen bond should be calcium sulfate and hydrochloric acid;

c correct. Solution: 1 According to the law of conservation of mass, the mass of oxygen generated is; 15 grams of grams = grams.

2 Let the mass of potassium permanganate be x

2kmno4=k2mno4+mno2+o2

x 316:32= x=

So the purity of potassium permanganate in the sample is: grams divided by 15 grams and multiplied by 100% =

This is just the third year of junior high chemistry, it is recommended that you read the book carefully, the teacher has definitely talked about it in class, and it is very troublesome to type.

2CO+2NO=catalyst=2CO2+N2

According to the conditions provided, it can be seen that B2 replaces A2, A2 replaces C2, and D2 replaces B2, so D2 is the most active, that is to say, the oxidizing D2>B2>A2>C2 reducibility can be known A > B, C>A, B>D (according to the reduction agent The reducing agent is greater than the reduction product is inferred) So the reduction C>A>B>d The others can also be reasoned according to these two relations, and the answer C is correct.

The answer is: acadbb (all questions can be found on the subject website).

When producing tons of nano2, n(nano2) =

The ratio of the amount of substances of nano2 and nano3 is 2:1, then n(nano3) = 1 104mol, and it can be seen from the conservation of Na atom that 2N(Na2CO3) = N(nano2) + N(nano3), m(Na2CO3) = (2 104mol + 1 104mol).

12 106g mol=, so the answer is:

According to the conservation of sodium ions, when nano2 is t, nano2 is.

Na2CO3 is 15000mol, and the mass is 15000*106=159000g=tons.

Aluminum hydrochloride magnesium.

You can use the special value method. Add 24 times 27 grams of magnesium or aluminum to each cup, and if the balance is balanced, the amount of hydrogen emitted from both beakers must be the same. This condition only occurs when hydrochloric acid is insufficient.

At this point, magnesium may be exactly finished, and aluminum must be left. 2.Hydrochloric acid overdose.

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