<span>The answer is the first option. Enzyme and substrate bind using a lock-and-key mechanism. Enzymes act on a specific substrate and a substrate needs a specific enzyme, this is what is called a lock-and-key mechanism. Enzymes and substtates are like a key and a lock, one is for each other.</span>
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Water<span> is capable of dissolving a variety of different substances, which is why it is such a good </span>solvent. Water dissolves more than any other liquid, therefor we called it the Universal Solvent.
The answer is 37.5 moles
The explanation:
1- when we have the mass of SO3 in Kg so, first we have to convert it to grams:
mass = 3 * 1000 = 3000 g
2- we need to get the molar mass of SO3 :
molar mass of SO3 = 32 + (16*3)
= 80 g/mol
3- then we can use this formula to get number of moles:
moles = mass / molar mass
= 3000 g / 80 g/mol
= 37.5 moles
Formula units in 450 g of 
is 1.93 × 10²⁴ formula units.
<u>Explanation:</u>
First we have to find the number of moles in the given mass by dividing the mass by its molar mass as,
Now, we have to multiply the number of moles of Na₂SO₄ by the Avogadro's number, 6.022 × 10²³ formula units/mol, so we will get the number of formula units present in the given mass of the compound.
3.2 mol × 6.022 × 10²³ = 1.93 × 10²⁴ formula units.
So, 1.93 × 10²⁴ formula units is present in 450g of Na₂SO₄.
