Question

What is the number of moles in 500 L of He gas at STP?

0.05
0.2
22
90
What is the percent of the composition of chromium BaCrO4?
4.87%
9.47%
20.5%
25.2%
What is the empirical formula of a substance that is 53.5% C, 15.5% H, 31.1% N by weight
C3HN2
C4H14N2
C2H7N
CH4N7
The product of a combination reaction is Ba(OH)2. If one of the reactants is H2O, what is the other reactant?
Ba2O
BaO
BaH
BaO2
Which of the following is true about single replacement reactions
They are restricted to metals
They involve a single product
Two reactants produce two products
Any metal replaces any other metal.



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Answer 1

1 90

29.47%

3 C4H14N2

4 BaO2

Answer 2

Step-by-step explanation:

1) At STP, 1 mol of gas occupies 22.4 L of volume.

1 L of volume will be occupied by :
`(1)/(22.4 L) mol`

Then, 500 L of volume will be occupied by:

`](1)/(22.4 L)* 500L =22.32 mol\approx 22 mol`

There will be 22 moles in 500 L of helium gas at STP.

2) Molecular mass of barium chromate= 253.37 g/mol

Atomic mass of chromium= 52 g/mol

Percentage of an element in a compound:

`\frac{\text{Number of atoms of element}* \text{Atomic mass of element}}{\text{molecular mass of element}}* 100`

Percentage of chromium:

`(1* 52 g/mol)/(253.37 g/mol)* 100=20.5\%`

20.5% is the percentage of chromium in the given molecular formula.

3)The empirical formula of a substance that is 53.5% C, 15.5% H, 31.1% N by weight.

In 100 g of substance, mass of carbon = 53.5 g

Moles of carbon =
`(53.5 g)/(12 g/mol)=4.45 mol`

In 100 g of substance, mass of hydrogen= 15.5 g

Moles of carbon =
`(15.5 g)/(1 g/mol)=15.5 mol`

In 100 g of substance, mass of nitrogen= 31.1 g

Moles of carbon =
`(31.1 g)/(14 g/mol)=2.22 mol`

For empirical formula, divide smallest number of moles of an element from all the constituting moles of the elements.

Carbon =
`(4.45 mol)/(2.22 mol)=2.0`

Hydrogen =
`(15.5 mol)/(2.22 mol)=6.9\appriox 7`

Nitrogen =
`(2.22 mol)/(2.22 mol)=1`

The empirical formula is
`C_2H_7N_1`.

4) Combination reaction is a type of a chemical reaction in which two or more reactant reacts together to give single product.

`A+B+C\rightarrow ABC`

Oxide of metals are basic in nature and when they dissolved in water they form basic solution of their respective hydroxide.So, barium hydroxide is made by dissolving barium oxide(BaO) in water.

`BaO+H_2O\rightarrow Ba(OH)_2`

5)Replacement reaction is defined as chemical reaction in which an element displaces another element from its single compound.

`A+BC\rightarrow AC+B`

Since, there are two reactants , out of which 1 is reactant compound. Both the reactants reacts to give two products.