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1 year ago

Provided is a list of five different substances. How many of these substances are elements?.

Chemistry

1 answer:

Lina20 [59]1 year ago

6 0

Answer:

118

Explanation:

Of these 118 elements, 94 occur naturally on Earth. Six of these occur in extreme trace quantities: technetium, atomic number 43; promethium, number 61; astatine, number 85; francium, number 87; neptunium, number 93; and plutonium, number 94.

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Is it possible for the equivalence point of a titration to not be at pH 7? Explain your answer.

lara31 [8.8K]

<span>The reason it will be 7 for some titrations is that when you titrates a strong acid with a strong base for example HCl and NaOH the salt formed is conjugate base of strong acid and will be a very weak base
That means that it cannot produce any OH^-1 and all the H+ has been converted to water.The only source of H+ or OH is water with a Ka of 10^-14 so the pH = -log [H+]=-log 10^-7 = 7
second reason is
When you titrates a weak acid with strong base at equivalence point
only a water solution of the conjugate base exists

CH3COOH + NaOH ----- Na+ CH3COO^-1 + H2O
Since the conjugate base is the conjugate base of a weak acid it will hydrolyze in water like so
for instance Na+ CH3COO^-1 + HCl---- CH3COOH + NaCl the equivalence point will be way BELOW 7 and in the case of above will be less than 5. So pH of 7 at equivalence point is only reached in strong acid strong base titrations.
hope this helps</span>

5 0

2 years ago

Read 2 more answers

a cube of iron (cp = 0.450 j/g•°c) with a mass of 55.8 g is heated from 25.0°c to 49.0°c. how much heat is required for this pro

krek1111 [17]

Q = ?

Cp = 0.450 j/g°C

Δt = 49.0ºC - 25ºC => 24ºC

m = 55.8 g

Q = m x Cp x Δt

Q = 55.8 x 0.450 x 24

Q = 602.64 J

hope this helps!

7 0

2 years ago

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Substance

ipn [44]

Answer:

lithium 3

Explanation:

This is because lithium has three protons

6 0

2 years ago

A is a d-aldohexose and B is an L-aldohexose. they afford the same optically active aldaric acid after dilute nitric acid oxidat

Alexeev081 [22]

Answer:

D-Glucose and L-Glucose

Explanation:

Aldohexose are the sugars which have six number of carbons and ends up in having an aldehyde group at one end. When dilute nitric acid is treated with any of them, the molecule gets oxidized (gets oxygen) and therefore turns into carboxylic acid.

The name of A is D-Glucose, and B is L-Glucose. Please find the structural formula attached.

8 0

2 years ago

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How many moles of gas X are present if the gas has a volume of 2dm³ at room temperature and pressure? Give your answer to 2 deci

bezimeni [28]

Answer:

Approximately $0.08\; \rm mol$ , assuming that this gas is an ideal gas.

Explanation:

Look up the standard room temperature and pressure: $25\; \rm ^{\circ}C$ and $P = 101.325 \; \rm kPa$ .

The question states that the volume of this gas is $V = 2\; \rm dm^{3}$ .

Convert the unit of all three measures to standard units:

$\begin{aligned} T &= 25\; \rm ^{\circ}C \\ &= (25 + 273.15)\; \rm K \\ &= 293.15\; \rm K\end{aligned}$ .

$\begin{aligned}P &= 101.325\; \rm kPa \\ &= 101.325 \; \rm kPa \times \frac{10^{3}\; \rm Pa}{1\; \rm kPa} \\ &= 1.01325 \times 10^{5}\; \rm Pa\end{aligned}$ .

$\begin{aligned}V &= 2\; \rm dm^{3} \\ &= 2 \; \rm dm^{3} \times \frac{1\; \rm m^{3}}{10^{3}\; \rm dm^{3}} \\ &= 2 \times 10^{-3}\; \rm m^{3}\end{aligned}$ .

Look up the ideal gas constant in the corresponding units: $R \approx 8.31\; \rm m^{3}\cdot Pa \cdot mol^{-1} \cdot K^{-1}$ .

Let $n$ denote the number of moles of this gas in that $V = 2\; \rm dm^{3}$ . By the ideal gas law, if this gas is an ideal gas, then the following equation would hold:

$P \cdot V = n \cdot R \cdot T$ .

Rearrange this equation and solve for $n$ :

$\begin{aligned}n &= \frac{P \cdot V}{R \cdot T} \\ &\approx \frac{1.01325 \times 10^{5}\; {\rm Pa} \times 2 \times 10^{-3}\; {\rm m^{3}}}{8.31 \; {\rm m^{3} \cdot Pa \cdot mol^{-1} \cdot K^{-1}} \times 293.15\; {\rm K}} \\ &\approx 0.08\; \rm mol\end{aligned}$ .

In other words, there is approximately $2\; \rm mol$ of this gas in that $V = 2\; \rm dm^{3}$ .

6 0

2 years ago