doesn't she
isn't it
has he
wasn't he
aren't they
is it
must he
isn't she
don't they
hasn't he
do they
didn't he
did she
isn't it
didn't he
was it
does she
doesn't he
didn't he
do they
didn't they
aren't there

$n_{MgO} = 0,15(mol)$
$MgO + 2HCl \to MgCl_2 + H_2O$
$n_{MgCl_2} = n_{MgO} = 0,15(mol)$
$n_{HCl} = 2n_{MgO} = 0,3(mol) \Rightarrow m_{dd\ HCl} = \dfrac{0,3.36,5}{10,95\%} = 100(gam)$
Sau phản ứng :
$m_{dd} = 100 + 6 = 106(gam)$

$C\%_{MgCl_2} = \dfrac{0,3.95}{106}.100\% =26,89\%$

a: 0,861

b: 6500

c: 0,04

d: 400

`861000 cm^3=0,861 m^3`

`6,5 dm^3=6500 cm^3`

`40 m^3= 40000dm^3`

`2/3 dm^3=400 cm^3`

I

1 play

2 get

3 are learning

4 are going to

II

1 book => books

2 on => in

3 have => to have

4 going => go

III

1 - B

2 - C

3 - D

4 - A

IV

1 What a beautiful girl!

2 How far is it from Viet Tri to Ha Noi?

4 We often skip rope at recess

5 How much does this book cost?

V

1 Yes, they do

2 They play football, badminton and table tennis

3 Yes, they do

4 They feel happy

3.1:

Ô tô đi hết 1h50'+40'=2h30'

3.2:

Ô tô đi hết:

17h50'-15h15'

=2h35'