Предмет: Химия, автор: Яна67

К раствору объемом 153,5 мл с массовой долей гидроксида калия 16% и плотностью 1,14г/мл прилили раствор объемом 86,8 мл с массовой долей серной кислоты 20% и плотностью 1,14 г/мл. Определите массу образованной соли

Ответы

Автор ответа: prevedd91

2KOH + H2SO4 = K2SO4 + 2H2O
mp-pa(KOH)=V*p=153.5*1.14=175г
m(KOH)=mp-pa*ω=174.99*0.16=28г
mp-pa(H2SO4)=V*p=86.8*1.14=99г
m(H2SO4)=mp-pa*ω=99*0.2=19.8г
n(KOH)=m/M=28/56=0.5 моль (в избытке, считаем по серной кислоте)
n(H2SO4)=m/M=19,8/98=0.2 моль
из уравнения видно, что n(H2SO4)=n(K2SO4)
m(К2SO4)=n*M=0.2*174=34.8 г

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Increasingly over the last few years we have become familiar with, the range of small electronic gadgets that come under the heading ‘smart’ accessories. Joggers, for example, run with heart-rate monitors, and shop assistants carry pocket-sized computers.

As a scientist at Massachusetts Institute of Technology’s Media Lab, Rosalind Picard tries out all kinds of is smart accessories before they go on the market. One of these was the so-called ‘frown headband’. It came as a shock to Rosalind to realise just how often she frowned. Stuck in a traffic jam recently, waiting for the cars to move forward, Rosalind kept hearing the sounds of the tiny sensor inside the band worn around her forehead - each time she frowned in frustration, the sensor gave out a signal.

Headbands that check facial expressions are just one of the things she and her colleagues have designed. Their aim is to make ready-to-wear items that both look good and give the wearer useful feedback. Body sensors, like those in Rosalind’s headband, can detect physical changes.

Another computer scientist, Steven Feiner, is working on a pair of glasses that will do more than help you to see. Are you one of those people who lack confidence when giving a talk to an audience? Look to the right and the glasses will flash your notes in front of your eyes. They could also prove useful for cooks who want to check a recipe without leaving sticky fingermarks all over their cookery books.

At the moment, Steven’s invention looks more like a pair of ski goggles than a pair of glasses. It’s a headset connected to a hand-held computer and a Global Positioning System (GPS) receiver, which tracks the wearer’s position. Students who don't mind being stared at have tried out the Star Trek-like device on campus. But Steven says that these head-worn displays will eventually get smaller, lighter and smarter as technology improves.

And, of course, this new technology has a fashionable as well as a useful application. A chemical engineer named Robert Langer has invented a new microchip that, if put inside a ring, can give off different scents according to a person’s mood. That, of course, may or may not appeal to you. And, in the end, it is shoppers, not scientists, who will determine which of these smart accessories will succeed as fashionable items and which are destined to join history’s long list of crazy inventions.

It is clear however, that as small computer displays get brighter and cheaper, they will pop up in all sorts of easily-wearable accessories, even in the buttons on your coat. What’s more, this is something that’s going to happen a lot sooner than we all expect.

1. When Rosalind wore the headband, she was surprised at …

A how well the sensor worked.

B how affected she was by the traffic.

C how strong the signal was.

D how comfortable it was to wear.

2. What does ‘Their’ in the text refer to?

A facial expressions

B headbands

C colleagues

D ready-to-wear items

3. Steven’s glasses will help people who are giving a talk by …

A telling them if they forget to say things.

B checking how nervous they’re feeling.

C signalling if they make a mistake.

D helping them to remember things.

4. What is the current problem with Steven’s glasses?

A where they are worn

B how much they cost

C what they look like

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A It is unlikely to work successfully.

B It is a bad use of new technology.

C He is sure people will laugh at it.

D He is uncertain whether people will buy it.

6. In general, what does the writer think about ‘smart’ accessories?

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B Much more research is needed into them.

C Only a few of them will prove to be useful.

D They will only affect the lives of certain people.

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