Предмет: Химия, автор: suiseihosimati

к 250г 20 проц ного раствора хлорида натрия добааили 40 г воды определите массовую долю соли в полученном растворе

Ответы

Автор ответа: Bogdanychteren
1
Ответ: масса чистого вещества равна произведению процента на массу раствора до добавления воды
250 г × 20%(0,2) =50г чистого вещества
Массовая доля равна отношению чистого вещества к раствору, однако туда добавили ещё воду массой 40 г, отсюда следует масса раствора равна 250+40=290г
Отсюда 50/290 =0,05434 округляем, получается 0,05 или 5 %

Bogdanychteren: Извините, там ошибка должно получиться 17%
Предыдущий вопрос
Следующий вопрос
Похожие вопросы
Предмет: Английский язык, автор: iljagapchich
ПОМОГИТЕ,ОЧЕНЬ СРОЧНО!
б) Past Indefinite или Past Continuous

1. How you (damage) your car so badly? – I (run) into a lamp-post yesterday. – I suppose you (drive) too quickly or were not looking where you (go).

2. As he (get) into the bus it (start) suddenly and he (fall) backwards on to the road.

3. I (call) Paul at 7.00 but it wasn't necessary because he already (get) up.

4. She (walk) along Oxford Street when she (realize) that a man she had seen that afternoon (follow) her.

5. As I (cross) the road I (step) on a banana skin and (fall) heavily. I still (lie) on the road when I (see) a lorry approaching. Luckily the driver (see) me and (stop) the lorry in time.



в) Present Perfect или Present Perfect Continuous

l. This is the first time he (be) to London.

2. I only (hear) from him twice since he went away.

3. I (plant) the flowers, that's why my hands are dirty.

4. I (polish) this table all the morning but I am not satisfied with it yet.

5. He (teach) in this school for five years.

6. "I (teach) hundreds of pupils but I never (meet) such a hopeless class as this", our teacher used to say.



г) Future Indefinite или Future Continuous

1. I want to post this letter but I don't want to go out in the rain. – I (post) it for you. I am going out anyway as I have to take the dog for a walk.

2. The prima ballerina is ill so I expect her understudy (dance) instead.

3. This time next Monday I (sit) in a Paris cafe reading Le Figaro. – You (not read). You (admire) the sights of the city.

4. Wages have gone up, so I suppose prices (go up) too.

5. It is nearly autumn; soon the leaves (change) co-lour.

6. Mother (on phone): My son has just burnt his hand very badly.

Doctor: I (come) at once.
1 год назад
Предмет: Русский язык, автор: zenitovskiy2004
Как объяснить ошибку в слове столовый
1 год назад
Предмет: Русский язык, автор: Leonardo151
Помогите 1 и 2 упр, срочно, желательно и 3е
1 год назад
Предмет: Алгебра, автор: vazira39
Пожалуйста помогите
7 лет назад
Предмет: Английский язык, автор: llavepizza
Task 5. Read the article about robots. Choose the best word for each space.
Robots
Most people have seen films about robots, but robots are also used in real life. Robots can do 21) _________ different things. They can, for example, make things in factories 22) _______________help astronauts.
One new robot from Japan can 23) walk, run and climb stairs. Engineers hope that in thefuture24) robot will be able to help people in theirhomes.25)_________new robot is special because it can have a conversation with you. A Canadian scientist has just made a robot that has hands that can move in 24 different ways.
21.
A)
lots
B)
much
C)
many
22.
A)
or
B)
because
C)
if
23.
A)
ever
B)
even
C)
yet
24.
A)
some
B)
this
C)
these
25.
A)
other
B)
both
C)
another
7 лет назад