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which statement is false?
there are 100 cm in a
decameter.
there are 10 mm in a
centimeter.
there are 1000 meters
in a kilometer
there are 100 cm in a
meter.

False statement:

There are 100 cm in a  decameter.

Explanation:

Kilometer is the largest unit of length.

1 km = 1000 m

So, there are 1000 m in a kilometer.

The next larger unit is decameter.

1 dm = 10 m

So, there are 10 meters in a decameter.

The next larger unit is meter.

1 m = 100 cm

So, there are 100 cm in a meter,

We have, 1 dm = 10 m and 1 m = 100 cm

So, 1 dm = 10 100 cm = 1000 cm

So, there are 1000 cm in a decameter.

The next larger unit is centimeter.

1 cm = 10 mm

So, there are 10 mm in a centimeter.

Therefore, among all the options, the first option seems wrong because 1 decameter equals 1000 cm and not 100 cm.

it would be b. 6co2 + 6h2o --> c6h12o6 + 6o2

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