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3 years ago

What rules should you follow when adding and subtracting? Check all that apply.

Chemistry

1 answer:

GaryK [48]3 years ago

5 0

Answer:

The answer to this question would be:

2. The exponents need to be the same so the leading numbers can be added or subtracted.

3. The result has the same number of decimal places as the least precise number.

The exponent is the 10^x that used in scientific notation. .When adding 12.3* 10^5 with 34.56 * 10^4, you need to make the exponent same first. In this case, it would become 12.3* 10^5 + 3.456 * 10^5= 15.756* 10^5

The decimal place could be rounded up to the least precise number. I'm not sure with the significant figures but it seems to use the biggest one.

Explanation:

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3 years ago

Consider the acid-base neutralization reaction H2S(aq) + CN‒(aq) ⇌ HS‒(aq) + HCN(aq) For H2S, pKa = 7.0, and for HCN, pKa = 9.4.

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Answer:

Explanation:

To assess the strength of an acid or a base we need to consider the pKa or pKb. For an acid, the lower the pKa, the stronger the acid. For a base, the lower the pKb, the stronger the base.

<em>Which of the following statements is FALSE?</em>

<em>(a) H₂S is a stronger acid than HCN.</em> TRUE. The pKa of H₂S (7.0) is lower than the pKa of HCN (9.4).

<em>(b) CN⁻ is a stronger base than HS⁻.</em> TRUE. We can calculate the pKb of a base when we know the pKa of the conjugate acid using the following expression:

pKa + pKb = 14 ⇒ pKb = 14 - pka

The pKb of CN⁻ (4.6) is lower than the pKb of HS⁻(7.0) so it is a stronger base.

<em>(c) At equilibrium, the equilibrium position favors the reactants.</em> FALSE. In the reaction H₂S(aq) + CN⁻(aq) ⇌ HS⁻(aq) + HCN(aq), H₂S is the stronger acid and CN⁻ is the stronger base, so at the equilibrium the products are favored.

(d) At equilibrium, the equilibrium constant, Kc, is larger than 1. TRUE. Given the products are favored at the equilibrium, the equilibrium constant Kc is expected to be larger than 1 (the numerator is higher than the denominator).

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3 years ago