F4 Chemistry Questions(12Q=10MC + 2LQ)_手机数码

更新1:

3)1 mole of a substance is athe amount equal to the formula mass of the substance in g bthe mass of a substance divided by its molecular mass cthe amount = its molar mass 4)2g of O gas contains x molecules

then 28g of N gas present(N=140

O=160) ax b4x c8x d16x

更新2:

5)1775g of Cl contain x molecules

then 8g of Sulphur dioxide contain(O=160

S=320

Cl=355) ax/4 bx/2 cx d2x 6)The molecular formula of a gas is X3 If the Avogadro's no is L mol^-1

how many atoms are there in 48g of X3(X=160) a1/2L bL c2L d3L

更新3:

7)2g of Carbon monoxide gas contain x molecules

how many molecules are present in 1g of H gas(H=10

C=120

O=160) a35x b55x c7x d11x 8)Molecular formula of a gaseous element X is X2

then no of molecules in 112g of the gas(X=140

L=60210^23) a4 b8 c4L d8L

更新4:

9)3 moles of magnesium chloride contains a3moles of molecules b6moles of cations c6moles of anions d9moles of atoms 10)An oxide of X has the formula X2O31428g of this contains 756 of X

then the relative atomic mass of X(O=160) a120 b180 c270 d360

更新5:

LQ: 11)51g of Cacl2．nH20 gives 50 g of water on strong and bees CaCl2 on heatingFind n(O=160

Cl=355

Ca=400

Cu=635)

更新6:

12)A hydrated salt of copper contains 639% by mass of the anhydrous saltThe anhydrous salt has the following percentage position by mass: copper 398%

sulphur 200%

oxygen 402% Find the empirical formula of the hydrated salt (O=160

S=320

Cl=355

Ca=400

Cu=635)

更新7:

Last notice: the informations about the elements in the brackets are the Atomic masses of the elements

1 A

C 2 A

C 3A 4D 5B 6B 7C 8C 9C 10C 11 The molar mass of CaCl2 = 40+3552 g/mol =111 g/mol The amount of CaCl2 in 51g of CaCl2．nH2O = (51-5)g =01g Therefore the number of mole of CaCl2 = (01/111) mol =1/1110 mol Amount of H2O = 50 g Therefore the number of mole of H2O = 5/18 mol ___________CaCl2________________H2O______________________ Mole________1/1110 mol____________ 5/18 Mole Ration ____1_________________around 278 (277777777777777) Therefore the formula is CaCl2．278H2O THE QUESTION MAY BE WRONG AS IT IS IMPOSSIBLE TO HAVE SUCH COMPOUND 12 Let's consider the empirical formula of the anhydrous salt first We will consider there's 100g of the anhydrous salt

therefore there are 398g

20g and 402g of copper

sulphur and oxygen respectively ________________Cu______________S_______________O mass___________398 g____________20______________402 number of mole__398/635____________5/8____________201/80 Mole Ratio____around 1(1003)_______1___________around 4 (402) (We'll divide the numbers with the allest mole) Therefore the empirical formula is CuSO4 The molar mass of CuSO4 is 1595 g/mol Let's consider the hydrated salt In 100g of CuSO4．nH2O has 639 of CuSO4 and the rest are H2O

which is 361g _____________CuSO4______________________H2O ______________639_______________________361 Mole_________639/1595____________________361/180 Mole Ration______1________________________around 5 (50060) Therefore the empirical formula of the hydrated salt is CuSO4．5H2O

参考: Chem knowledge

解：

1、

a-b=2 ①

b-c=2 ②

由①+②得

a-c=4

∴(a-b)(b-c)(a-c)=2×2×4=16

2、

应该是已知 2x除以(2+8y)=1 求 x-4y

2x÷(2-8y)=1

2x=2+8y