1. bromine is a a. black solid b. red liquid c. colourless gas d. highly inflammable gas 2. the hardest substance available on earth is a. gold b. iron c. diamond d. platinum 3. the variety of coal in which the deposit contains recognisable traces of the original plant material is a. bitumen b. anthracite c. lignite d. peat 4. tetraethyl lead is used as a. pain killer b. fire extinguisher c. mosquito repellent d. petrol additive 5. which of the following is used as a lubricant? a. graphite b. silica c. iron oxide d. diamond

1.  B.  red liquid

2. C.  diamond

3.  D.  peat

4.  D.  petrol additive

5.  D.  diamond

Explanation:

1.B

2.C

3.D

4.D

5.A

as given the equation is

2al + 6 hcl > 2 alcl3 + 3 h2(g)

as per equation two moles of aluminum reacts with six moles of hcl to give two moles of alcl3 and three moles of hydrogen gas

given: three moles of al are present and 7 moles of hcl

for three moles of aluminum nine moles of hcl will be required

however as 7 moles of hcl are present so the limiting reagent is hcl

hcl is going to decide the number of moles of product formed

when six moles of hcl are present = 3 moles of h2 are formed

when one mole of hcl is present == 3/6 mole sof h2 will be formed

when 7 moles of hcl are present = 3 x 7/ 6 moles of h2 will be formed = 3.5 moles of h2