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3 years ago

What number do you never write as a coefficient?

Chemistry

1 answer:

N76 [4]3 years ago

4 0

Answer:

When no coefficient is written in front of a formula it is assumed to be 1. 4. Numbers appearing in the formulas are known as subscripts. These can never be changed when balancing the equation or you will change the identity of the substance.

Explanation:

1. Reactants go on the left hand side and products go on the right hand side of a chemical equation. Be sure to write the correct formulas for the reactants and products.

· Remember atoms are conserved in a chemical reaction. ie they are neither created or destroyed. So all the atoms in the reactants must end up somewhere among the products.

2. Count the number of atoms of each element, compound or ion in the reactants and products. If they are not equal proceed further.

3. Balance the atoms one at a time by placing coefficients in front of the formula so that the numbers of atoms of each element are equal on both sides of the equation. Remember atoms may exist in an element, compound or ion.

· It is usually easier to start with the atoms that occur in only one substance on each side of the equation.

· Balance the atoms that occur in compounds before attempting to balance atoms that occur in elemental form. e.g. H2, O2 or Cl2

· To make it easier if a polyatomic ion appears unchanged on both sides of the equation treat it as a whole unit.

· When no coefficient is written in front of a formula it is assumed to be 1.

4. Numbers appearing in the formulas are known as subscripts. These can never be changed when balancing the equation or you will change the identity of the substance.

· Remember with subscripts, any number to the right of parentheses multiplies each subscript within the parentheses.

eg Fe2(SO4)3 contains 2 Fe atoms, 3 S atoms and 12 O atoms.

5. Finally make sure that all the coefficients are in the smallest possible whole number ratio.

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2 H2 + O2= 2 H2O

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Answer:

the answer is 4.0moles

Explanation:

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The composition of a liquid-phase reaction 2A - B was monitored spectrophotometrically. The following data was obtained: t/min 0

o-na [289]

Answer:

1) The order of the reaction is of FIRST ORDER

2) Rate constant k = 5.667 × 10 ⁻⁴

Explanation:

From the given information:

The composition of a liquid-phase reaction 2A - B was monitored spectrophotometrically.

liquid-phase reaction 2A - B signifies that the reaction is of FIRST ORDER where the rate of this reaction is directly proportional to the concentration of A.

The following data was obtained:

t/min 0 10 20 30 40 ∞

conc B/(mol/L) 0 0.089 0.153 0.200 0.230 0.312

For a first order reaction:

$K = \dfrac{1}{t} \ In ( \dfrac{C_{\infty} - C_o}{C_{\infty} - C_t})$

where :

K = proportionality constant or the rate constant for the specific reaction rate

t = time of reaction

$C_o$ = initial concentration at time t

$C _{\infty}$ = final concentration at time t

$C_t$ = concentration at time t

To start with the value of t when t = 10 mins

$K_1 = \dfrac{1}{10} \ In ( \dfrac{0.312 - 0}{0.312 - 0.089})$

$K_1 = \dfrac{1}{10} \ In ( \dfrac{0.312 }{0.223})$

$K_1 =0.03358 \ min^{-1}$

$K_1 \simeq 0.034 \ min^{-1}$

When t = 20

$K_2= \dfrac{1}{20} \ In ( \dfrac{0.312 - 0}{0.312 - 0.153})$

$K_2= 0.05 \times \ In ( 1.9623)$

$K_2=0.03371 \ min^{-1}$

$K_2 \simeq 0.034 \ min^{-1}$

When t = 30

$K_3= \dfrac{1}{30} \ In ( \dfrac{0.312 - 0}{0.312 - 0.200})$

$K_3= 0.0333 \times \ In ( \dfrac{0.312}{0.112})$

$K_3= 0.0333 \times \ 1.0245$

$K_3 = 0.03412 \ min^{-1}$

$K_3 = 0.034 \ min^{-1}$

When t = 40

$K_4= \dfrac{1}{40} \ In ( \dfrac{0.312 - 0}{0.312 - 0.230})$

$K_4=0.025 \times \ In ( \dfrac{0.312}{0.082})$

$K_4=0.025 \times \ In ( 3.8048)$

$K_4=0.03340 \ min^{-1}$

We can see that at the different time rates, the rate constant of $k_1, k_2, k_3, and k_4$ all have similar constant values

As such :

Rate constant k = 0.034 min⁻¹

Converting it to seconds ; we have :

60 seconds = 1 min

∴

0.034 min⁻¹ =(0.034/60) seconds

= 5.667 × 10 ⁻⁴ seconds

Rate constant k = 5.667 × 10 ⁻⁴

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