O chumbo é obtido da galena (PbS) através da sequência de reações não balanceadas, apresentadas a seguir.

x PbS_(s) + y O_{2 (g)} -> z PbO_(s) + w SO_{2 (g)}

PbS_(s) + PbO_(s) -> Pb_(s) + SO_{2 (g)}

A soma dos coeficientes estequiométricos representados por x, y, z e w resulta no seguinte valor:

(UEFS)

Se infinitos quadrados, cujas áreas formam uma progressão geométrica decrescente de razão q pudessem ser empilhados, como na figura, e o quadrado da base tivesse uma área de 1m², a altura da pilha, em m seria:

A black woman born into slavery replaces a White slave owner on $ 20 note

Harriet Tubman – the 19th century abolitionist and suffragist who led dozens of slaves through the Underground Railroad to free states – is about to become the new face of the $ 20 bill, replacing slaveholder Andrew Jackson, the seventh president of the United States. The Treasury Department secretary Jack Lew announced the decision – which would make Tubman the first black American and second woman to appear on American paper currency – on Wednesday. [...] The idea of replacing Jackson with Tubman on the $ 20 by 2020 started with an online petition. Advocates of the idea liked its inherent symbolism – and 2020 marks the 100th anniversary of the constitutional amendment giving women the right to vote. [...] Jackson owned a property known as the Hermitage in Tennessee, a 1,000-acre cotton plantation that relied entirely on slave labor. [...] Tubman was born into slavery in Maryland, and was regularly beaten and whipped by her slave masters. She escaped, and later made 13 separate missions to rescue scores of enslaved families, helping them reach the free Northern states. [...]

Harriet Tubman é um dos grandes nomes que marcaram a história do mundo, sendo escolhida para estampar a nota de 20 dólares dos Estados Unidos por

Texto base:

Enunciado:

Na situação comunicativa da tira, a linguagem verbal de cada quadrinho constitui uma frase porque apresenta