1. underline the correct item.
i watched/ was watching a film when my cat jumped/ was jumping on me.
she was buying/ bought a new pair of shoes last sunday.
pete was sleeping/ slept while joe listened/ was listening to a new cd.
we were having/ had dinner when someone was knocking/ knocked on the door.
they were walking/ walked to school last monday because there was no bus.
mum was planting/ planted flowers when it started/ was starting to rain.
i ate/ was eating an apple while my sister drank/ was drinking some milk.
2. put when or while.
you can't imagine what happened yesterday while we were walking in the park.
we were walking there it started to rain.
it started to rain we went into the cafe.
we were sitting in the cafe a famous footballer came in.
we saw him everybody in the cafe jumped up and ran to him for the autographs.
i was running to him i stumbled my feet.
i was falling off i knocked the table and hit the footballer.
we saw that we were all together on the floor we started to laugh. at the end he presented me his t-shirt and an autograph. what a day!
3. put the verbs in brackets in the correct tense.
we went (go) shopping yesterday.
i (have) lunch while my mum -up).
jeff (watch) tv at 7 o'clock yesterday evening.
what / do) yesterday? - i (have) as very busy day. i (help) my granddad in the garden. we (dig) the garden all day long.
4. what did finn and sue did yesterday? use the cues and write a story. use the past simple or the past continuous.
be/ beautiful/ sunday morning - it was a beautiful sunday morning.
finn and sue/ decide/ to take/ their dog/ for a walk/ in the park
sue/ sit/ bench/ read/ magazine/ while/finn/ walk/ with the dog
in half an hour / finn/ come/ back/ alone
they/ look/ for dog/ everywhere/ but/ not find / him
when/ get dark/ they/ decide/ return home
when/ they/ arrive home/ dog/ lie in front of the door
Дано:
Н — ген, що визначає нормальне зсідання крові;
h — ген, що визначає гемофілію;
ХНХН — здорова жінка;
XHXh — здорова жінка, носій гена гемофілії;
XhXh — жінка-гемофілік, нежиттєздатна;
ХНУ — здоровий чоловік;
XhY — чоловік-гемофілік.
Імовірність народження дітей-гемофіліків — ?
F XHXh — здорова дівчинка (25%)
XhXh — дівчинка-гемофілік (25%)
XHY — здоровий хлопчик (25%)
XhY — хлопчик-гемофілік (25%)
Відповідь. Вірогідність народження в цій сім’ї дітей, хворих на гемофілію, становить 50 % для хлопчиків і 50 % для дівчаток.
Дано:
m(HNO3) = 45 г
m(CaO) = 24 г
m(соли) – ?
Составим уравнение реакции
2HNO3 + CaO = Ca(NO3)2 + H2O
Отсюда видно, что кто-то из реагентов может быть в избытке
Рассчитаем количество вещества каждого из реагентов по формуле n = m / M (*)
n(HNO3) = 45 г / 63 г/моль = 0,714 моль
n(CaO) = 24 г / 56 г/моль = 0,429 моль
Отсюда видим, что n(HNO3) / 2 < n(CaO), то есть CaO в избытке, считаем по азотной кислоте
n(Ca(NO3)2) = n(HNO3) / 2 = 0,714 моль / 2 = 0,357 моль
Рассчитаем массу из формулы (*)
m(соли) = n(Ca(NO3)2) * M(Ca(NO3)2) = 0,357 моль * 164 г/моль = 58,55 г
ответ: 58,55 г